The Project Gutenberg eBook of Grasses This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online at www.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook. Title: Grasses A handbook for use in the field and laboratory Author: H. Marshall Ward Release date: January 6, 2015 [eBook #47898] Language: English Credits: Produced by Chris Curnow, Turgut Dincer and the Online Distributed Proofreading Team at http://www.pgdp.net (This file was produced from images generously made available by The Internet Archive) *** START OF THE PROJECT GUTENBERG EBOOK GRASSES *** Produced by Chris Curnow, Turgut Dincer and the Online Distributed Proofreading Team at http://www.pgdp.net (This file was produced from images generously made available by The Internet Archive) CAMBRIDGE BIOLOGICAL SERIES. GENERAL EDITOR:--ARTHUR E. SHIPLEY, M.A., F.R.S. FELLOW AND TUTOR OF CHRIST’s COLLEGE, CAMBRIDGE. GRASSES. CAMBRIDGE UNIVERSITY PRESS WAREHOUSE, C. F. CLAY, MANAGER. London: FETTER LANE, E.C. Edinburgh: 100, PRINCES STREET. [Illustration] ALSO London: H. K. LEWIS, 136, GOWER STREET, W.C. Leipzig: F. A. BROCKHAUS. New York: G. P. PUTNAM’S SONS. Bombay and Calcutta: MACMILLAN & CO. LTD. [_All Rights reserved._] GRASSES A HANDBOOK FOR USE IN THE FIELD AND LABORATORY. BY H. MARSHALL WARD, SC.D., F.R.S. LATE PROFESSOR OF BOTANY IN THE UNIVERSITY OF CAMBRIDGE. CAMBRIDGE: AT THE UNIVERSITY PRESS. 1908 _First Edition 1901 Reprinted 1908_ PREFACE. The following pages have been written in the hope that they may be used in the field and in the laboratory with specimens of our ordinary grasses in the hand. Most of the exercises involved demand exact study by means of a good hand-lens, a mode of investigation far too much neglected in modern teaching. The book is not intended to be a complete manual of grasses, but to be an account of our common native species, so arranged that the student may learn how to closely observe and deal with the distinctive characters of these remarkable plants when such problems as the botanical analysis of a meadow or pasture, of hay, of weeds, or of “seed” grasses are presented, as well as when investigating questions of more abstract scientific nature. I have not hesitated, however, to introduce general statements on the biology and physiological peculiarities of grasses where such may serve the purpose of interesting the reader in the wider botanical bearings of the subject, though several reasons may be urged against extending this part of the theme in a book intended to be portable, and of direct practical use to students in the field. I have pleasure in expressing my thanks to Mr R. H. Biffen for carefully testing the classification of “seeds” on pp. 135-174, and to him and to Mr Shipley for kindly looking over the proofs; also to Mr Lewton-Brain, who has tested the classification of leaf-sections put forward on pp. 72-82, and prepared the drawings for Figs. 21-28. That errors are entirely absent from such a work as this is perhaps too much to expect: I hope they are few, and that readers will oblige me with any corrections they may find necessary or advantageous for the better working of the tables. The list of the chief authorities referred to, which students who desire to proceed further with the study of grasses should consult, is given at the end. I have pleasure in acknowledging my indebtedness to the following works for illustrations which are inserted by permission of the several publishers:--Stebler’s _Forage Plants_ (published by Nutt & Co.), Nobbe’s _Handbuch der Samenkunde_ (Wiegandt, Hempel and Parey, Berlin), Harz’s _Landwirthschaftliche Samenkunde_ (Paul Parey, Berlin), Strasburger and Noll’s _Text-Book of Botany_ (Macmillan & Co.), Figuier’s _Vegetable World_ (Cassell & Co.), Lubbock’s _Flowers, Fruits and Seeds_ (Macmillan & Co.), Kerner’s _Natural History of Plants_ (Blackie & Son), and Oliver’s _First Book of Indian Botany_ (Macmillan & Co.). It is impossible to avoid the question of variation in work of this kind, and students will without doubt come across instances--especially in such genera as _Agropyrum_, _Festuca_, _Agrostis_ and _Bromus_--of small variations which show how impossible it is to fit the facts of living organisms into the rigid frames of classification. It may possibly be urged that this invalidates all attempts at such classifications: the same argument applies to all our systems, though it is perhaps less disastrous to the best Natural Systems which attempt to take in large groups of facts, than to artificial systems selected for special purposes. Perhaps something useful may be learned by showing more clearly where and how grasses vary, and I hope that the application to them of these preliminary tests may elucidate more facts as we proceed. H. M. W. CAMBRIDGE, _April_, 1901. CONTENTS. CHAPTER I. PAGE THE VEGETATIVE ORGANS 1 CHAPTER II. THE VEGETATIVE ORGANS (_continued_) 17 CHAPTER III. GRASSES CLASSIFIED ACCORDING TO THEIR VEGETATIVE CHARACTERS 39 CHAPTER IV. ANATOMY AND HISTOLOGY 62 CHAPTER V. GRASSES CLASSIFIED ACCORDING TO THE ANATOMICAL CHARACTERS OF THE LEAF 72 CHAPTER VI. GRASSES IN FLOWER 83 CHAPTER VII. GRASSES GROUPED ACCORDING TO THEIR FLOWERS AND INFLORESCENCES 99 CHAPTER VIII. THE FRUIT AND SEED 119 CHAPTER IX. CLASSIFICATION OF GRASSES BY THE “SEEDS” (GRAINS) 135 BIBLIOGRAPHY 175 INDEX, GLOSSARY AND LIST OF SYNONYMS 177 CHAPTER I. THE VEGETATIVE ORGANS. That grasses are interesting and important plants is a fact recognised by botanists all the world over, yet it would appear that people in general can hardly have appreciated either their interest or their importance seeing how few popular works have been published concerning their structure and properties. Apart from their almost universal distribution, and quite apart from the fascinating interest attaching to those extraordinary tropical giants, the Bamboos, West Indian Sugar-cane, the huge Reed-grasses of Africa, the Pampas-grasses of South America; and from the utilitarian value of the cereals--Maize, Rice, Wheat and other corn, &c.--everyone must be struck by the significance of the enormous tracts of land covered by grasses in all parts of the world, the Prairies of North America and the Savannahs of the South, the Steppes of Russia and Siberia, and the extensive tracts of meadow and pasture-land in Europe being but a few examples. Although in the actual number of species the Grass family is by no means the largest in the vegetable kingdom, for there are far more Composites or Orchids, the curious sign of success in the struggle for existence comes out in grasses in that the number of _individuals_ far transcends those of any other group, and that they have taken possession of all parts of the earth’s surface. Some species are cosmopolitan--e.g. our common Reed, _Arundo Phragmites_; while others--e.g. several of our native species of _Festuca_ and _Poa_--are equally common in both hemispheres. On the whole the Tropics afford most species and fewest individuals, and the temperate regions most individuals. Considering their multifarious uses as fodder and food, for brewing, weaving, building and a thousand other purposes, it is perhaps not too much to say that if every other species of plant were displaced by grasses of all kinds--as many indeed gradually are--man would still be able to supply his chief needs from them. The profound significance of the grass-carpet of the earth, however, comes out most clearly when we realise the enormous amounts of energy daily stored up in the countless myriads of green blades as they fix their carbon. By decomposing the carbon-dioxide of the air in their chlorophyll apparatus by the action of the radiant energy of the sun, they build up starches and sugars and other plant-substances, which are then consumed and turned into flesh by our cattle and sheep and other herbivorous animals, and so furnish us with food. The whole theory of agriculture turns on this pivot, and the by no means small modicum of truth in such sayings as “All flesh is grass,” and that the man who can make two blades of grass grow where one grew before deserves well of his country, obtains a larger significance when it is realised that the only real gain of wealth is that represented by the storage of energy from without which comes to us by the action of green leaves waving in the sunshine. The true Grasses, comprising the Natural Order Graminaceæ--also written Gramineæ--are often popularly confounded with other herbs which possess narrow green ribbon-like leaves, or even with plants of very different aspects--e.g. Cotton-grass (_Eriophorum_) and other Sedges, and the names Rib-grass (_Plantago_), Knot-grass (_Polygonum_), Scorpion-grass (_Myosotis_) and Sea-grass (_Zostera_), as well as the general usage of the word grass to signify all kinds of leguminous and other hay-plants in agriculture, point to the wider use of the word in former times. This has been explained by the use of the words _gaers_, _gres_, _gyrs_, and grass in the old herbals to indicate any kind of small herbage. In view of the importance of our British grasses in agriculture, I have here put together some results of observation and reading in the hope that they may aid students in recognising easily our ordinary agricultural and wild grasses. During several years of work in the fields, principally directed at first to the study of the parasitic fungi on grasses, and subsequently to that of the importance of grasses in forestry and agriculture, and to the variations they exhibit, the need of some guide to the identification of a grass at any time of the year, whether in flower or not, forced itself on the attention, and although a botanist naturally turns to a good Flora when he has the grass in flower, as the best and quickest way of ascertaining the species, it soon became evident that much may be done by the study of the leaves and vegetative parts of most grasses. Indeed some are recognisable at a glance by certain characters well known to continental observers: in the case of others the matter is more difficult, and perhaps with a few it is impossible to be certain of the species from such characters only. Nevertheless, while the best means for the determination of species are always in the floral characters so well worked up in the Floras of Hooker, Bentham and others, there is unquestionably much value in the characters of the vegetative organs also, as the works of Jessen, Lund, Stebler, Vesque and others abroad, and Sinclair, Parnell, Sowerby and others in this country attest. Almost the only plants confounded with true grasses by the ordinary observer are the sedges and a few rushes. Apart from the very different floral structures, there are two or three easily discoverable marks for distinguishing all our grasses from other plants (Fig. 1). The first is their leaves are arranged in _two rows_, alternately, up the stems; and the second that their stems are circular or flattened in section, or if of some other shape they are _never triangular_ and _solid_[1] (Figs. 6 and 7). Moreover the leaves are always of some elongated shape, and without leaf-stalks[2], but pass below into a _sheath_, which runs some way down the stem and is nearly always perceptibly split (Figs. 8-13). Further, the stems themselves are usually terete, and distinctly hollow except at the swollen nodes, and only branch low down at the surface of the ground or below it[3]. [Illustration: Fig. 1. A plant of Oat (_Avena_), an example of a typical grass, showing tufted habit and loose paniculate inflorescence (reduced). Figuier.] All our native grasses are herbaceous, and none of them attain very large dimensions. In the following lists I term those small which average about 6-18 inches in the height of the tufts, whereas those over 3 feet high may be termed large, the tufts being regarded as in flower. The sizes cannot be given very accurately, and starved specimens are frequently found dwarfed, but in most cases these averages are not far wrong for the species freely growing as ordinarily met with, and in some cases are useful. I have omitted the rare species throughout, and in the annexed lists have added the popular names. LARGE GRASSES. (Over 3 feet.) _Milium effusum_ (Millet-grass). _Digraphis arundinacea_ (Reed-grass). _Aira cæspitosa_ (Tufted Hair-grass). _Arrhenatherum avenaceum_ (False Oat). _Elymus arenarius_ (Lyme-grass). _Bromus asper_ (Hairy Brome). _B. giganteus_ (Tall Brome). _Festuca elatior_ (Meadow Fescue). _F. sylvatica_ (Reed Fescue). _Glyceria aquatica_ (Reed Sweet-grass). _G. fluitans_ (Floating Sweet-grass). _Arundo Phragmites_ (Common Reed). MEDIUM GRASSES. (1-3 feet.) _Phleum pratense_ (Timothy). _Avena pratensis_ (Perennial Oat-grass). _Anthoxanthum odoratum_ (Sweet Vernal). _Alopecurus agrestis_ (Slender Foxtail). _A. pratensis_ (Meadow Foxtail). _Agrostis alba_ (Fiorin). _Psamma arenaria_ (Sea Mat-grass). _Avena flavescens_ (Yellow Oat-grass). _Holcus lanatus_ (Yorkshire Fog). _Hordeum sylvaticum_ (Wood Barley). _H. pratense_ (Meadow Barley). _Agropyrum repens_ (Couch-grass). _A. caninum_ (Fibrous Twitch). _Lolium italicum_ (Italian Rye-grass). _Brachypodium sylvaticum_ (Wood False-Brome). _B. pinnatum_ (Heath False-Brome). _Bromus erectus_ (Upright Brome). _B. sterilis_ (Barren Brome). _B. arvensis_ (Field Brome). _Festuca ovina_ (var. _rubra_, &c.). (Sheep’s Fescue). _F. elatior_ (var. _pratensis_). (Meadow Fescue.) _Dactylis glomerata_ (Cock’s-foot). _Cynosurus cristatus_ (Crested Dog’s-tail). _Poa pratensis_ (Meadow-grass). _P. trivialis_ (Rough stalked Meadow-grass). _P. nemoralis_ (Wood Poa). _Molinia cærulea_ (Flying Bent). _Melica nutans_ (Mountain Melick). _M. uniflora_ (Wood Melick). SMALL GRASSES. (6-18 inches.) _Phleum arenarium_ (Sand Cat’s-tail). _Alopecurus geniculatus_ (Marsh Foxtail). _Agrostis canina_ (Brown Bent). _Aira flexuosa_ (Wavy Hair-grass). _Aira canescens_ (Grey Hair-grass). _A. præcox_ (Early Hair-grass). _A. caryophyllea_ (Silvery Hair-grass). _Nardus stricta_ (Moor Mat-grass). _Hordeum murinum_ (Wall Barley). _H. maritimum_ (Sea Barley). _Lolium perenne_ (Rye-grass). _L. temulentum_ (Darnel). _Bromus arvensis_ (var. _mollis_). (Field Brome). _Festuca ovina_ (Sheep’s Fescue). _F. Myuros_ (Rat’s-tail Fescue). _Briza media_ (Quaking-grass). _Poa maritima_ (Sea Poa). _P. annua_ (Annual Meadow-grass). _P. compressa_ (Flattened Meadow-grass). _P. alpina_ (Alpine Poa). _P. bulbosa_ (Bulbous Poa). _Triodia decumbens_ (Heath-grass). _Kœleria cristata_ (Crested Kœleria). The roots of our grasses are almost always thin and _fibrous_ and are adventitious from the nodes, frequently forming radiating crowns round the base and easily pulled up, and usually broken in the process; but in the case of a few moor grasses--especially _Nardus_ (Fig. 2) and _Molinia_--the roots are so tough and thick (_stringy_) as to resist breakage very efficiently. In stoloniferous grasses a similar difficulty of removal may be caused in a slighter degree by the underground stems. In a few cases, e.g. _Alopecurus bulbosus_ (Fig. 3), _Poa bulbosa_, _Phleum pratense_ and _P. Bœhmeri_, _Arrhenatherum avenaceum_, and to a slighter extent in _Poa alpina_ and one or two others, the lowermost internodes and sheaths of the stems may be swollen and stored with food-materials, and a sort of _tuber_ or _bulb_ results; this is especially apt to occur in dry sandy soils. In old lawns, pastures, &c., the roots of _Poa annua_ and others may have nodules on them due to the presence of certain small Nematode worms, _Heterodera_. [Illustration: Fig. 2. _Nardus stricta._ Plant showing tufted habit, and simple spikate inflorescence, with pointed spikelets all turned towards one side (secund) on the rachis (reduced). Note also the bristle-like (setaceous) leaves at length reflexed. Parnell.] [Illustration: Fig. 3. _Alopecurus geniculatus_, var. _bulbosus_. Plant (reduced) showing habit, bulbous shoots and cylindrical spike-like inflorescences (Foxtail type). Notice the inflated sheaths, and the “kneed” lower parts of the ascending stems. Parnell.] Grasses are annual, biennial, or perennial, and it is often of importance to know which. The point may usually be determined by examining the shoots. If all the shoots have flowering stems in them, and are evidently of the current year, the grass is an annual; but if any shoots have leaves only, it is either biennial or perennial: to determine which is not always easy, but in perennial grasses there will generally be evident remains of older leaf-bases and shoots, and if there are distinct underground stolons or creeping rhizomes as well the point may be considered decided, and the grass is perennial, as is the case with most of our important species. If all the shoots are barren, the grass is a biennial in its first year of growth: if all have flowering stems in them, but show traces of old leaf-bases of the previous year, then the grass is a biennial in its second year. The proof of biennial character is not always easy, however, and a few grasses may be either annual or biennial, or biennial or perennial, according to conditions--e.g. species of _Hordeum_, _Bromus_, &c. In the following lists I have given the duration of the principal grasses, where the character is especially important. ANNUALS. _Phleum arenarium._ _Aira præcox._ _A. caryophyllea._ _Hordeum murinum._ _H. maritimum._ _Lolium temulentum._ _Festuca Myurus._ _Briza minor._ _Poa rigida._ _P. annua._ ANNUALS which may become biennial or perennial. _Alopecurus geniculatus._ _Hordeum pratense._ _Lolium perenne._ _L. italicum_ (may be perennial). _Bromus asper_ (may be perennial). _B. sterilis._ _B. arvensis_ (may be perennial). PERENNIALS. _Holcus lanatus._ _H. mollis._ _Nardus._ _Hordeum sylvaticum._ _Agropyrum._ _Brachypodium._ _Bromus erectus._ _B. giganteus._ _Festuca ovina._ _F. elatior._ _F. sylvatica._ _Dactylis._ _Cynosurus cristatus._ _Briza media._ _Milium._ _Anthoxanthum._ _Digraphis._ _Phleum pratense._ _Alopecurus pratensis._ _Agrostis alba._ _A. canina._ _Psamma._ _Aira cæspitosa._ _A. flexuosa._ _A. canescens._ _Avena pratensis._ _A. flavescens._ _Arrhenatherum._ _Glyceria aquatica._ _G. fluitans._ _Poa maritima._ _P. compressa._ _P. pratensis._ _P. trivialis._ _P. nemoralis._ _P. alpina._ _P. bulbosa._ _Molinia._ _Melica._ _Triodia._ _Kœleria._ _Arundo._ [Illustration: Fig. 4. _Catabrosa aquatica._ Plant showing the creeping habit, rooting nodes, and paniculate inflorescence (reduced). Parnell.] The rhizome of a perennial grass is continued sympodially by means of buds branching from the lowermost joints of the flowering shoots, and some importance is attached to the mode of spreading of these lateral sprouting shoots. The buds always arise in the axils of the lower leaf-sheaths--i.e. they are _intra-vaginal_. If they remain intra-vaginal during further growth, the shoots are forced upwards and only _tufts_ (Fig. 2) are formed, except in so far as such shoots may fall prostrate on the surface of the ground later, and throw out roots from their nodes, and so act as _runners_ or offsets, or put out a few roots &c. as they ascend through the soil. But in many cases the buds soon burst through the leaf-sheaths, and develope as _extra-vaginal_ shoots, and may then run horizontally as underground _stolons_. Only creeping grasses of these latter kinds can rapidly cover large areas[4]: the grasses with intra-vaginal shoots only can only make tufts or “tussocks.” Several peculiarities in the habits of grasses depend on these facts. The following are the most important creeping, or _stoloniferous_ species, contrasted with the much more common _tufted_ and the far rarer grasses with _runners_ above ground (Fig. 4). Some of these (_Elymus_, _Psamma_, &c.) are of great importance as sand-binders.— With intra-vaginal branches only. _Lolium_--slightly stoloniferous. _Festuca elatior_--slightly stoloniferous. _Avena flavescens_--slightly stoloniferous. _Phleum pratense_--no stolons, but may be bulbous. _Dactylis_--no stolons. _Festuca ovina_--no stolons. _Poa alpina_--no stolons. _Cynosurus_--no stolons. With extra-vaginal shoots. _Arrhenatherum_--short stolons, sometimes bulbous. _Holcus lanatus_--creeping. _Alopecurus pratensis_--long stolons. _Anthoxanthum_--slightly stoloniferous. _Agrostis alba_ (var. _stolonifera_)--long stolons and runners. _Digraphis_--long stolons. _Poa pratensis_--long stolons. _P. trivialis_--runners only. _Festuca heterophylla_, Lam.--a variety of _F. ovina_ with slight stolons. _F. rubra_ (Linn.)--a variety of _F. ovina_ with long stolons. _Bromus erectus_--no stolons. _B. inermis_--long stolons. Creeping below ground and truly stoloniferous. _Agropyrum._ _Elymus._ _Psamma._ _Poa pratensis._ _P. compressa._ _Agrostis alba_ (var. _stolonifera_). _Alopecurus pratensis._ _Brachypodium_ (slightly). _Bromus erectus_ (slightly). _Festuca ovina_ (var. _rubra_, Linn.). _F. elatior_ (slightly). _Briza_ (slightly). _Glyceria._ _Poa maritima._ _Melica._ _Arundo._ Tufted Grasses. _Milium._ _Agrostis alba_ (on downs, &c.). _Aira cæspitosa._ _A. flexuosa._ _A. canescens._ _A. præcox._ _A. caryophyllea._ _Avena pratensis_ (slightly creeping). _Arrhenatherum._ _Nardus_ (Fig. 2). _Hordeum sylvaticum._ _Lolium._ _Bromus._ _Festuca ovina_ (except some varieties). _F. sylvatica._ _F. Myurus._ _Dactylis._ _Cynosurus._ _Poa rigida._ _P. annua._ _P. trivialis._ _P. nemoralis._ _P. alpina._ _P. bulbosa._ _Molinia._ _Triodia._ _Kœleria._ Creeping above ground (with runners). _Holcus lanatus._ _Alopecurus geniculatus._ _Agrostis alba_ (var. _stolonifera_). _Hordeum pratense_ (slightly). _H. murinum_ (slightly). _Catabrosa_ (Fig. 4). _Cynodon_ (Fig. 5). Hackel has pointed out that a distinction must be drawn between the true nodes of the _culm_, and the swellings often found at the base of the _sheaths_ themselves over these: the latter are often conspicuous when the former are inconspicuous--e.g. most species of _Agrostis_, _Avena_, _Festuca_, &c. The nodes are of importance in the description of a few species only--e.g. they are usually dark coloured in certain _Poas_ such as _P. compressa_ and _P. nemoralis_; they are sharply bent in _Alopecurus geniculatus_, and may be so in other species if “layed” by wind, rank growth, &c. A point of considerable classificatory value is the shape of the transverse section of the shoot, which is correlated with the mode of folding up of the young leaf-blades. [Illustration: Fig. 5. _Cynodon Dactylon._ Plant (reduced) showing creeping and stoloniferous habit, and peculiar inflorescence of digitate spikes. Parnell.] In most grasses the blades are _convolute_--i.e. rolled up like the paper of a cigarette, one edge over the other--and the section of the shoot is round (Fig. 7). In some cases, however, the leaves are _conduplicate_--i.e. each half of the lamina is folded flat on the other, the upper sides being turned face to face inwards, with the mid-rib as the hinge--and in this case the shoots are more or less compressed (Fig. 6). [Illustration: Fig. 6. _Dactylis glomerata._ Transverse section of a leaf-shoot (× 5). _A_, conduplicate leaf-blade. _B_, sheath. Stebler.] [Illustration: Fig. 7. _Digraphis arundinacea._ Transverse section of a leaf-shoot (× 5). _A_, sheath. _B_, convolute leaves. Compare Fig. 14. Stebler.] In these latter cases the transverse section may be elliptical--e.g. _Poa pratensis_ and _P. alpina_, _Briza_, &c., or more flattened and linear-oblong--e.g. _Glyceria fluitans_--with the flattened sides straight, or the section is oval but pointed more or less at each end owing to projecting keels and leaf-edges, and the form is _naviculate_--e.g. _Glyceria aquatica_, _Dactylis_ (Fig. 6)--or, the sides being less flattened, more or less _rhomboidal_ as in _Poa trivialis_. In _Melica_ the leaves are convolute and the shoot-section _quadrangular_. Flat, and usually sharp-edged shoots. _Dactylis glomerata_ (Fig. 6). _Poa trivialis_, _P. annua_, _P. pratensis_, _P. compressa_, _P. maritima_, and _P. alpina_. _Glyceria aquatica_ and _G. fluitans_. _Avena pubescens._ _Lolium perenne._ CHAPTER II. THE VEGETATIVE ORGANS (_continued_). The leaves of all our grasses consist of the _blade_, which passes directly into the _sheath_, without any petiole or leaf-stalk (Fig. 1). The sheath is usually obviously _split_, and so rolled round the internode that one edge overlaps the other, but in the following grasses the sheath is either quite _entire_, or only slit a short way down, the two edges being fused as it were for the greater part of its length. Sheath more or less entire. _Glyceria aquatica_ and _G. fluitans_. _Melica uniflora_ and _M. nutans_. _Dactylis glomerata._ _Poa trivialis_ (Fig. 8), _P. pratensis_, _P. alpina_. _Sesleria cærulea._ _Bromus_ (all the species). _Briza media_ and _B. minor_. In some cases--e.g. _Arrhenatherum_, _Bromus asper_, and _Holcus lanatus_--the sheath is marked with a more or less prominent ridge down its back, due to the continuation of the _keel_ of the leaf. The sheath may also be glabrous or hairy, and grooved or not. A few grasses are so apt to develope characteristic colours in their sheaths, especially below, that they may often be recognised in winter by this peculiarity. Sheaths coloured. _Lolium_--all red. _Holcus_--red with purple veins. _Festuca elatior_--red. _Cynosurus_--yellow. _Alopecurus pratensis_, and _A. agrestis_--violet-brown, &c. _Festuca ovina_, var. _rubra_--red. [Illustration: Fig. 8. _Poa trivialis. A_, base of blade. _B_, ligule. _C_, sheath. _D_, culm (× about 3).] [Illustration: Fig. 9. _Alopecurus pratensis. A_, base of blade. _B_, ligule. _C_, sheath. Slightly magnified.] [Illustration: Fig. 10. _Avena flavescens._ Lettering as before (× 2). Note the split sheath, the hairs and ridges. Stebler.] At the junction of the blade with the sheath there is in most cases a delicate membranous upgrowth of the former, more or less appressed to the stem, and called the _Ligule_ (Figs. 8-13). Its use is probably to facilitate the shedding of water which has run down the leaf; and so lessen the danger of rotting between the sheath and stem: possibly the shelves and ears commonly met with at the base of the lamina (Fig. 12) aid in the same process. This ligule may be long or short, acute or obtuse, toothed or entire, or it may be reduced to a mere line, or tuft of hairs, or even be obsolete, and is of considerable value in classification--e.g. the ligule is obsolete or wanting in _Melica_, _Festuca ovina_, _F. Myurus_, _F. elatior_, _Kœleria_ and _Panicum_. It is represented by a tuft of hairs in _Molinia_, _Triodia_ and _Arundo_. [Illustration: Fig. 11. _Lolium perenne. A_, base of lamina, _B_, ligule. _C_, sheath (× 3). Note the low ribs, and absence of hairs (glabrous).] [Illustration: Fig. 12. _Festuca elatior_, var. _pratensis_. _A_, base of lamina. _B_, the extremely short ligule, with pointed ears. _C_, sheath (× 3).] [Illustration: Fig. 13. _Festuca ovina. A_, base of lamina. _B_, ligular ears. _C_, sheath (× about 4). Stebler.] Our other ordinary grasses have a more or less well-developed _membranous_ ligule (Fig. 8). The leaf-blade is long or short, broad or narrow, but always of some elongated form such as linear, linear-lanceolate or linear-acuminate, or subulate, setaceous, &c., varying as to the degree of acuteness of the apex, and the tapering of the base. In the following native grasses the _form_ of the lamina affords a useful character. The base tapers to the sheath below--i.e. the leaf is more or less linear-lanceolate--in _Molinia_, _Brachypodium_, _Melica_, _Milium_, _Kœleria_, and the very rare _Hierochloe_; less distinctly so in _Bromus asper_ and species of _Hordeum_. The base is rounded in _Arundo_. In the following cases the leaves are setaceous, due to the very narrow blade remaining permanently folded or inrolled at its edges, and usually being thickened and hardened also (Figs. 13 and 18). The habitat of these moor-and heath-grasses suggests that these are no doubt adaptations to prevent excessive evaporation by the exposure of too large a surface--e.g. various species of _Aira_, _Festuca ovina_, _F. Myurus_ and allies, _Nardus_, and several other species; whereas, conversely, the thin flat leaves of shade-grasses facilitate exposure to light and transpiration. In _Avena pratensis_ and _Agrostis canina_ some of the leaves are involute and subulate, and the thickened leaves of _Poa maritima_ also are turned up at the edges, and are +U+-shaped in cross-section. As we shall see later the degree of inrolling of many grass leaves varies with circumstances. In most others the blades are either flat (Figs. 8-12), or more or less conduplicate on the mid-rib. The latter case occurs, for example, in grasses with flattened shoots, especially at the lower part of the blade--e.g. _Lolium perenne_, _Dactylis_, _Glyceria_, and some species of _Poa_, and the cross-section of the leaf below, just before it enters the sheath, is +V+-shaped. In _Glyceria_ the leaf-bases may show yellow or brownish triangles. Further characters of the leaves are derived from their texture, apex, margins, mid-ribs and venation, hairiness, and especially the presence and characters of the longitudinal ridges which run along the upper or lower surface in many cases. The venation is parallel from base to apex in nearly all our grasses, but such is not always the case--e.g. in the exotic _Panicum plicatum_ the mid-rib, which enters the leaf with several vascular bundles, gives off strong and weak veins below, which first diverge and then run in arches which converge upwards: this leaf is also remarkable in being _plaited_ (plicate) in vernation. In _Arundo Donax_ also the veins, though approximately parallel, do not all run to the apex of the tapering leaf; the outer ones end above in the margins and are shorter than the mid-rib. As regards _texture_, the leaves of most grasses are thin and herbaceous; but in some they are dry and harsh to the touch. They are thin and dry in _Agropyrum caninum_, _Hordeum pratense_, _H. murinum_, _Avena pratensis_, &c., very hard and leathery (_coriaceous_) in _Psamma_, _Nardus_, species of _Festuca_, _Aira_, _Agropyrum junceum_, _Elymus_, &c. In aquatic grasses like _Glyceria_, the leaf is almost spongy owing to the large air-chambers developed in the tissues. These are easily visible with a lens. The _apex_ is in most cases slender and tapering--_acuminate_; but in some it is merely brought to a point (_acute_) as in _Catabrosa_, _Glyceria_ and several species of _Poa_ and _Avena_, &c., usually flat, but somewhat hooded or curved up in some Poas. In cases where the leaves are _setaceous_ or _subulate_, the apex is like a thin tapering bristle, and even flatter leaves may be so inrolled at the tips as to have the apex prolonged into a sharp needle-like _pungent_ or _spinescent_ point--e.g. _Hordeum pratense_, _Avena pratensis_ to a slight extent, and pronounced in _Elymus_, &c. In _Sesleria_ the apex is rounded with a short, sharp, prickle-like median projection (_mucronate_). The passage of blade into sheath has already been described, but the base of the blade may have its margins projecting as horizontal shelves, like a Byron collar, round the sides of the throat of the sheath, sometimes tinged with yellow or pink--e.g. _Lolium_, _Holcus_, _Bromus inermis_, _Hordeum_; the ends of these may project as _auricles_ or ears--e.g. _Festuca elatior_, _Elymus_, _Agropyrum_, _Anthoxanthum_, _Bromus asper_, _Hordeum_, &c. In _Festuca ovina_ the ears are short, stiff, and erect (Fig. 13). The margin may be perfectly even, as in most grasses, or it is more or less _scabrid_ or _scaberulous_, as in _Aira cæspitosa_, _Poa maritima_, _Festuca elatior_, _Avena pratensis_, _Agrostis_, _Milium_, _Phleum_, _Briza_, the minute teeth (_serrulæ_) pointing up or down. The surface may be bright green, or glaucous, harsh, hairy or glabrous, and is not uncommonly also _scabrid_, like a file or emery-paper, and sometimes only when rubbed in one direction up or down, owing to the minute teeth being directed all one way. These teeth are developed on the ridges. All our ordinary grass leaves are parallel-veined, and the vascular strands (the veins) can usually be seen on holding the leaf up to the light. In most cases the tissue is raised over the veins, as ridges or “ribs,” and according to the height of these ridges the thinner parts between look like deep or shallow furrows (cf. Figs. 8-16 and Chapter IV.). If the leaf is held up to the light the ridges appear _dark_ in proportion to their opacity--i.e. height or thickness--and the furrows _light_ in proportion to the thinness of the tissues there. If the contrast is very great, as in _Aira cæspitosa_ (Fig. 23), the furrows seem like transparent sharp lines, and when, as in _Poa_, which is practically devoid of ridges, the difference of thickness is small they appear merely as fine striæ. These characters must be determined on the fresh leaves, however, because the contraction in drying draws the ridges closer together and tends to obliterate the lines. [Illustration: Fig. 14. _Digraphis arundinacea._ Transverse section of mid-rib and half the leaf (× about 6).] [Illustration: Fig. 15. _Holcus lanatus._ Transverse section of leaf-blade (× 10).] [Illustration: Fig. 16. _Cynosurus cristatus._ Transverse section of the leaf-blade (× 20). Stebler.] The ridges are almost always evident--_Catabrosa_, _Poa_, and _Avena_ furnishing the chief exceptions--and are nearly invariably on the upper surface: they are below in _Melica_, however; and their relative numbers, heights and breadths, section--acute, rounded, or flattened--furnish valuable characters; as also does the coexistence or absence of hairs, asperities, &c. [Illustration: Fig. 17. Transverse section of the leaf of _Festuca elatior_, var. _pratensis_ (× 12).] [Illustration: Fig. 18. Ditto of the leaf of _F. ovina_ (× 15).] [Illustration: Fig. 19. Ditto of the leaf of _F. ovina_, var. _rubra_ (× 35).] [Illustration: Fig. 20. _Festuca ovina_, var. _rubra_. Transverse section of the blade of an upper leaf (× 35). Stebler.] A very interesting anatomical adaptation is met with in the leaves of many grasses which grow in dry situations (xerophytes) such as on sandy sea-shores, exposed mountains and so forth. When the air is moist, in wet weather or in the dews, and the sun’s rays not too powerful, the leaf is spread out with its upper surface flat or nearly so, but when the scorching sun and dry air or winds prevail, the leaves fold or roll up, with the upper sides apposed or overlapping inside the hollow cylinder thus made. In such leaves some of the upper epidermal cells, either next the mid-rib (_Sesleria_ &c.) or between the other ribs (_Festuca_ &c.) are large and very thin-walled, full of sap when distended, and so placed that as they lose water by evaporation they contract, and so draw together the two halves of the lamina (_Sesleria_) or each ribbed segment (_Festuca_), thus causing the infolding or inrolling (see Chapter IV). Not only from the structure and actions of these motor-cells, but also from the fact that the stomata are on the upper surfaces and thus protected, and that the lower surfaces which alone are exposed to the drought are defended by hard and impenetrable tissues, we must look upon these as adaptations to the xerophytic conditions. Leaves prominently ridged. _Elymus._ _Psamma._ _Aira cæspitosa._ _Lolium._ _Cynosurus_ (Fig. 16). _Agrostis._ _Alopecurus._ _Glyceria fluitans._ _Kœleria._ _Festuca elatior._ _Festuca Myurus_ (var. _sciuroides_). _Melica_ has ridges on the _lower_ surface. Ridges are less prominent in _Phleum pratense_, _Briza_, _Agropyrum_, _Triodia_, _Arrhenatherum avenaceum_. Leaves practically devoid of ridges. _Poa_--all common species. _Glyceria aquatica._ _Catabrosa aquatica._ _Avena pratensis._ In some grasses the tissue over the mid-rib is considerably raised and strengthened on the dorsal side of the blade as a “keel.” Keel more or less prominent. _Arrhenatherum_ (sheath keeled). _Poa_ (all except _P. maritima_). _Dactylis._ _Bromus._ _Bromus asper_ (sheath keeled, often a white line). _Holcus lanatus_ (slight and decurrent) (Fig. 15). _Digraphis_ (Fig. 14). _Glyceria._ Most grasses are glabrous, but there are a number in which hairs are nearly always a prominent feature. It must be remarked, however, that with grasses, as with other plants, the character of pubescence is apt to vary with the situation. In general it may be stated that a hairy grass tends to become more glabrous in a moist situation, and more pubescent in a dry one, but the rule is by no means absolute. In some cases,--e.g. _Avena pubescens_, _A. flavescens_, _Agropyrum_, the hairs are almost entirely confined to the crests of the ridges (Figs. 10, 15). The following is a list of hairy grasses. HAIRY GRASSES. _Holcus_ (Fig. 15). _Molinia cærulea._ _Brachypodium sylvaticum._ _Agropyrum_ (variable). _Bromus asper._ _B. mollis._ _Hordeum._ _Anthoxanthum._ _Avena flavescens_ (Fig. 10). _A. pubescens._ _Triodia._ _Kœleria._ To a less extent. _Festuca sciuroides_ (on ribs). _Melica._ Grasses as a rule are devoid of strong scents[5] or tastes, but _Anthoxanthum_ has a faint but distinct sweet odour, especially as it dries--it is one of the grasses which give the scent to new-mown hay--and a bitter flavour, and _Milium_, _Hierochloe_ and _Holcus_ are also more or less bitter. _Spartina stricta_ emits a strong unpleasant odour. The habitat of grasses is of great importance as an aid to determination. No one would expect to find a sea-shore grass growing in a beech-forest, or an aquatic grass on a dry chalk-down; but they are even more true to their habitats than this, and I append the following lists of habitats of British grasses as of use in determining them, though it is not pretended that the limits are absolute. In the following list “pasture-grass” (P) means useful for grazing, and “meadow-grass” (M) one that is especially valuable for mowing--i.e. for hay. A “weed” (W) is used in its agricultural sense for a grass not useful and not wanted on cultivated land, though often found there. MEADOW-AND PASTURE-GRASSES. (P and M) _Dactylis glomerata_ (fields, &c.). (P and M) _Poa trivialis_ (meadow and pasture). (W) _Bromus arvensis_ (cultivated and waste places, meadow and pasture). (W) _B. sterilis_ (ruderal). (P and M) _Poa pratensis_ (meadow and pasture). (W) _Briza media_ (meadow and pasture). (P) _Avena pratensis_ (meadow and pasture, especially hilly). (P) _A. pubescens_ (var.)--dry. (P and M) _Lolium perenne_ (meadow, pasture and waste places). (P and M) _L. italicum_ (valuable culture grass). (P) _Cynosurus cristatus_ (downs). (M and P) _Festuca elatior_ (meadow and moist pasture, banks and river-sides). (W) _Agrostis alba and A. canina_ (pasture and waste places, wet or dry). (P and M) _Alopecurus pratensis_ (meadow and pasture). (W) _A. geniculatus_ (moist meadows and marshes). (P and M) _Phleum pratense_ (meadow and pasture). (P) _Arrhenatherum avenaceum_ (meadow, hedges and copse). (P and M) _Anthoxanthum odoratum_ (fields generally). (W) _Hordeum pratense_ (moist meadow and pasture). (W) _Holcus lanatus and H. mollis_ (meadow, pasture and waste). (P and M) _Avena flavescens_ (dry meadow and pasture). (W) _Avena fatua_ (corn-weed). (P) _Festuca ovina_ (light limestone pastures and chalk downs). SHADE-GRASSES. Found in woods, copses, &c., under shade. _Melica uniflora_ (woods, &c.). _Bromus asper_ (hedges, thickets, and edges of woods). _B. giganteus_ (hedges and woods). _Aira cæspitosa_ (moist shade and damp hedges). _Poa nemoralis_ (woods, shady places and damp mountain rocks). _Milium effusum_ (moist woods, &c.). _Agropyrum caninum_ (woods and shady places). _Hordeum sylvaticum_ (woods and copse). _Brachypodium sylvaticum_ (woods, hedges and thickets). _Arrhenatherum avenaceum_ (meadows, hedges and copse). _Festuca sylvatica_ (mountain woods). AQUATIC AND SEMI-AQUATIC GRASSES. Found in wet ditches, ponds, and on marshes, river-banks, &c. _Glyceria fluitans_ (wet ditches and slow waters). _G. aquatica_ (wet ditches and shallow waters). _Alopecurus geniculatus_ (moist meadow and marsh lands). _Digraphis arundinacea_ (river-banks, marshes). _Arundo Phragmites_ (wet ditches, marshes and shallow waters). _Molinia cærulea_ (wet heaths and moors, woods and waste places). _Triodia decumbens_, _Agrostis alba_, _Catabrosa_ and _Calamagrostis_. MOOR-AND HEATH-GRASSES. Downs and dry hill-pastures. _Nardus stricta_ (moors, heaths and hilly pastures). _Aira flexuosa_ (heaths and hill pastures). _Molinia cærulea_ (wet heathy moors, woods and waste places). _Kœleria cristata_ (dry pasture). _Triodia decumbens_ (dry heathy and hilly pastures). _Festuca ovina_ (hilly pastures--especially dry and open--rarer in moist situations). _Agrostis vulgaris_ and _A. canina._ MARITIME OR SEASIDE GRASSES. _Poa maritima_ (maritime). _P. distans_ (sandy pastures and wastes near sea). _Elymus arenarius_ (coasts). _Psamma arenaria_ (coasts). _Poa bulbosa_ (waste places in S.E. of England). _Agropyrum junceum_ (coasts). _Hordeum maritimum_ (S. and E. coast). _Phleum arenarium_ (coasts). RUDERAL OR VAGABOND GRASSES. Waste places, walls, road-sides and dry sandy situations. _Molinia cærulea_ (wet, heathy moors, woods and waste places). _Festuca Myurus_ (waste places, walls, road-sides). _F. ovina_ (hilly pastures and especially dry, rarely moist situations). _Aira caryophyllea_ (sandy and hilly pastures). _Aira præcox_ (sandy and hilly pastures). _Poa distans_ (sandy wastes near the sea). _P. compressa_ (dry, barren, waste ground). _P. annua_ (cultivated and waste lands and fields). _Agropyrum repens_ (fields and waste places). _Hordeum murinum_ (waste places and road-sides). _Holcus lanatus_ (meadow, pasture, and waste lands). _H. mollis_ (same--rarer). _Alopecurus agrestis_ (waste lands and roads in S. of England). _Lolium perenne_ (meadows, pastures and waste places). _L. temulentum_ (fields and waste places, not common). _Bromus sterilis_ (on way-sides, &c.). _B. arvensis_ (cultivated and waste meadows and pastures). _Poa rigida_ (dry, rocky places). It is also often useful to know whether a grass is rare or local, especially for the purpose we have in view, and I have therefore drawn up the following list of rare, local or introduced foreign grasses either not noticed at all, or only referred to incidentally in this work. In many cases these introduced foreign grasses have sprung up from seeds brought over in cargoes of hay, wool, and other products and packing materials, which in part accounts for their occurrence only near certain sea-ports, manufacturing towns and so forth. Such plants are frequently termed ballast plants. Foreign plants are also introduced in seed, as mixtures or impurities, and frequently escape from corn-fields &c. _Leersia oryzoides_ (ditches of Hants., Sussex and Surrey). _Panicum sanguinale_ (S. England). _P. verticillatum_ (fields in S. and E.). _P. glaucum_ (rarely introduced). _Hierochloe borealis_ (Thurso only). _Phleum alpinum_ (Highlands only). _P. Bœhmeri_ (Eastern counties, rare). _P. asperum_ ” ” ” _Phalaris canariensis_ (rare weed). _Alopecurus alpinus_ (Highlands). _Mibora verna_ (Anglesea and Channel Islands). _Lagurus ovatus_ (Suffolk coasts). _Polypogon monspeliensis_ (rare, in S. England near sea). _P. littoralis_ (salt marshes S. England). _Agrostis setacea_ (dry heaths of S. Wales). _A. Spica-venti_ (sandy fields of E. counties). _Gastridium lendigerum_ (fields and waste places in S. Wales and Norfolk). _Calamagrostis Epigeios_ (moist glades &c. in Scotland). _C. lanceolata_ (moist shades, scattered in England). _C. stricta_ (bogs, &c., very rare). _Cynodon Dactylon_ (waste and cultivated lands near sea in Scotland). _Spartina stricta_ (salt marshes S. and E. coast). _Lepturus incurvatus_ (scattered on shores). _Bromus maximus_ (Jersey). _B. madritensis_ (roads and waste, Scotland and Tipperary). _B. inermis_ (introduced from Hungary). _Lolium italicum_ (introduced from Lombardy). _Festuca uniglumis_ (Irish and S.E. coast). _Poa procumbens_ (waste ground near sea). _P. loliacea_ (sandy sea-shores). _P. laxa_ (Ben Nevis, &c.). _P. alpina_ (Highlands and N.). _Catabrosa aquatica_ (shallow pools and ditches, scattered). Finally, a few words may be said on a subject still in its infancy--that of Indicator-plants. In many cases certain plants are found so confined to certain classes of soil, that foresters and agriculturists have claimed to be able to infer from their presence the presence or absence of certain chemical or other constituents of soils: on the contrary we find other plants so universally distributed without reference to the quality of the soil, that they are not indicative. The latter are often termed _ruderal_ or _vagabonds_ (see p. 29). Without attempting too rigid a classification of Grasses in this connection--which would be premature in this early state of our knowledge--the following remarks are at least generally true. A few grasses are Indicators of chalk and limestone--e.g. _Briza media_, _Kœleria cristata_, and the exotic species _Stipa pennata_ and _Melica ciliata_. The following are said to indicate a sufficiency of potassium salts, In moister soils. _Digraphis arundinacea._ _Phleum pratense._ _Avena pubescens._ _Arundo Phragmites._ _Molinia cærulea._ _Glyceria fluitans._ In drier soils. _Anthoxanthum odoratum._ _Alopecurus pratensis._ _Agrostis alba._ __Holcus lanatus.__ _Arrhenatherum._ _Kœleria cristata._ _Briza media._ _Dactylis glomerata._ _Cynosurus cristatus._ _Poa pratensis._ _P. trivialis._ _P. compressa._ _Festuca elatior._ _Lolium perenne._ Grasses like _Bromus arvensis_ indicate the existence of clay in the soil. While the following are indicative of sand, _Aira caryophyllea._ _A. præcox._ _A. canescens._ _Festuca ovina._ _Bromus sterilis._ And only if the sandy soil is moist and of better quality, owing to a certain proportion of humus, the following, _Anthoxanthum odoratum._ _Agrostis alba._ _Dactylis glomerata._ _Arrhenatherum avenaceum._ _Avena pubescens._ _Poa pratensis._ That the soil contains considerable quantities of common salt--sodium chloride--may be inferred if the following grasses occur, _Psamma arenaria._ _Elymus arenarius._ _Hordeum maritimum._ _Agropyrum junceum_, &c. The existence of much humus is indicated by such shade grasses as _Melica uniflora._ _M. nutans._ _Milium effusum._ _Bromus giganteus._ _B. asper._ _Brachypodium sylvaticum._ Whereas soils known as “sour,” though containing much vegetable remains, may be suspected if the following grasses abound on them, _Aira cæspitosa._ _Nardus stricta._ _Alopecurus geniculatus._ _Molinia cærulea_; especially if sedges and rushes coexist with them. When cuttings are made in forests, such grasses as the following are very apt to appear, and may do harm to young plants, _Festuca ovina_ and varieties. _Agrostis alba._ _Holcus mollis._ _Aira flexuosa_, &c. The grasses more especially indicative of particular classes of forest-soils are chiefly the wood-species (see p. 28), and need not be further specified. In gaps, borders, and copses--half-shade--we find several common grasses--e.g. _Anthoxanthum odoratum._ _Agrostis alba._ _Aira flexuosa._ _Holcus lanatus._ _Arrhenatherum avenaceum._ _Triodia decumbens._ _Dactylis glomerata._ _Festuca rubra._ _Brachypodium pinnatum._ _Hordeum sylvaticum._ Whereas _Poa nemoralis_, _Festuca sylvatica_, _Agropyrum caninum_, _Melica_, _Milium_, _Bromus asper_, _B. giganteus_, _Brachypodium sylvaticum_, are more likely to be met with in the deep shade inside the forest. On the other hand there are vagabond grasses which seem to show no signs of preference for one soil over another--e.g. _Poa annua_--though in some cases these _ruderal_ plants indicate the presence of rotting substances, on ash-heaps and rubbish of various kinds. With reference to the above, however, the student must not forget that very complex relations are concerned in changes of soil, shade, moisture, elevation, &c. and that although experienced observers can draw conclusions of some value from the presence of _numerous species and individuals_ on a given soil, no one must conclude too readily that a soil is so and so, from observing solely that a particular kind of grass will grow there. An excellent example of what may be done by applying such knowledge as exists of the habits of grasses, is afforded by the historic case of the planting up of shifting sand-dunes with species like _Psamma arenaria_, _Elymus arenarius_, _Agropyrum junceum_, &c. (together with sand-binding species of sedges) and so not only fixing the sand, but preparing it for gradual afforestation with bushes and eventually trees, and so saving enormous tracts of land and sums of money, as has been done on the West coasts of France. Moreover, the action of ruderal plants--including grasses--is to completely alter the nature of the poor soil and gradually fit it for other plants. Coverings of grass greatly affect the actions of heat and sunshine on the surface soil, and modify the effects of radiation and evaporation, to say nothing of the penetrating and other effects of the roots. Rhizomes and stolons break up stiff soils; and every engineer and forester knows how useful certain grasses are in keeping the surface-soil from being washed down by heavy rains on steep hill-sides or embankments. On the other hand, luxuriant growths of tall grasses may do harm to young plants, by their action as weeds and especially as shade-plants; though foresters can employ them in the latter capacity, under restrictions, to shelter young trees from the sun. Again, too much dry grass near a forest offers dangers from fire; and it is a well known fact that certain injurious animals, e.g. mice and other vermin, are favoured by a covering of grass. Graminaceæ are for the most part chalk-fleeing plants, in spite of the fact that certain species can grow in very thin layers of soil on chalk downs. They must be regarded as requiring moderate supplies of humus as a rule, and even sand-loving grasses are not real exceptions. The physiognomy of the grasses has always been regarded as a striking one, and Humboldt classed it as one of his 19 types of vegetation. As is well known they are sociable plants, often covering enormous areas--prairies, alps, steppes, &c.--with a few species, alone or densely scattered throughout a mixed herbage. They also represent characteristically the sun-plants, the erect leaves exposing their surfaces obliquely to the solar rays, and being often folded and nearly always narrow. The dead remains of these sociable grasses are an important factor in protecting the soil against drought and in facilitating humification, as well as in covering up plants during long winters or dry seasons, keeping the ground warmer and moister, and generally lessening the effect of extremes. Many Graminaceæ are pronounced xerophytes, the epidermis often being developed as a water-storing tissue, while the erect leaves roll themselves in intense light, the stomata being situated accordingly. The halophytic strand-plants _Psamma arenaria_, _Elymus arenarius_, _Agropyrum junceum_, and other Dune-species, as well as species of _Aira_, _Festuca_, _Anthoxanthum_, _Stipa_, _Lygeum_, _Aristida_, &c. are examples. The heath-grasses--e.g. _Festuca ovina_, _Nardus stricta_, _Molinia cærulea_--also come under this category. Many of the strand-plants (halophytes) _Agropyrum_, _Psamma_, _Elymus_, are covered with waxy bloom, and have long rhizomes which bind the sand and form new soil, a property largely taken advantage of in certain forest operations. Other grasses, particularly annual species, show their adaptation to xerophytic habits by forming bulbous store-houses at the base of the culms--e.g. _Phleum arenarium_. Some Graminaceæ are hydrophytes, such as _Arundo_, _Glyceria_, &c., with large intercellular spaces in their tissues; while many species--e.g. _Aira cæspitosa_, _Agrostis canina_, _Molinia cærulea_--grow on wet moor-lands, forming perennial tufts, with or without creeping rhizomes. The mesophyte grasses are especially characteristic of what may be termed carpets--a lawn is a good example on a small scale, though of course we must remember that here the struggle for existence has been artificially interfered with more or less. Such carpets consist of the densely interwoven rootlets and rhizomes forming sod, and contain much humus from the accumulated débris of former years. These grass-carpets may be composed of nearly pure growths of a few species, or of very many different grasses and other herbage. They are common in Arctic regions, on Alps, and in temperate climates generally, where we know them as meadows, hay-fields, pasture and lawns. The Bamboos in the wider sense have a physiognomy of their own, e.g. in India, and may drive out most other plants and form dense undergrowths or jungle of interlaced stems and leaves and thorny shoots. Similar growths occur on the Andes and elsewhere in South America. In some parts of India and tropical Asia the taller bamboos form aggregates comparable to dense forests, and such forests are common on the banks of several large tropical rivers. Most of these Bamboos are xerophytes. Bamboos are neither confined to the tropics, nor to warmer regions, however, for species are known from distinctly cool regions--e.g. South America--or even from near the snow line--e.g. Chili, the Himalayas, Japan, &c., and the number of species known as hardy is increasing annually, as is evident on examining our larger English gardens. The permanence and character of extensive grasslands, especially prairies, savannahs, and steppes, are much affected by the periodical firing they are exposed to in the dry season, and large tracts of country in various parts of the world would doubtless bear forests or other vegetation if not thus fired, while in other cases the herbage would be differently constituted were firing discontinued. The following chapter embodies an attempt to classify our British grasses solely for purposes of identification when not in flower. It is not claimed that the arrangement is the best possible, nor that it is complete, and I need hardly say that corrections will be gratefully received. CHAPTER III. GRASSES CLASSIFIED ACCORDING TO THEIR VEGETATIVE CHARACTERS. I. SHEATHS ENTIRE EXCEPT WHERE THOSE OF LOWER LEAVES ARE BURST BY BRANCHES, &C. +A. Aquatics with the sheaths reticulated, owing to large air-cavities. Leaves equitant, linear acute, often floating.+ _Glyceria fluitans_ (Br.). Floating sweet grass. Somewhat coarse, but useful pasture in water-meadows and fens. Sweet-tasting. Section of sheathed leaves linear oblong; sheath striate or furrowed, keeled; leaf ribbed; ligule broad acute. Leaf-base with a yellow triangle. Smooth. _Glyceria aquatica_ (Sm.). Reed sweet grass. Especially given to growing in the water-courses and on banks instead of spreading in the water-meadows, &c. Sweet-tasting. Section of sheathed leaves broadly naviculate; sheath smooth, no keel; leaf not ribbed, thick and inflated with large air-cavities; ligule short. Leaf-base with a brown triangle. Margins and keel rather rough. These two species of _Glyceria_ are distinguished by their shoot-sections and the ridges of the leaves of _G. fluitans_: they often occur in the same ditch. They cannot readily be confused with others on account of their aquatic habit, and the characters given. The only other aquatic or semi-aquatic species are forms of _Catabrosa_, _Digraphis_, _Arundo_, _Alopecurus geniculatus_, _Molinia cærulea_ and the rare _Calamagrostis_. The ligule and flat shoots with closed sheaths alone suffice to distinguish it from the round and split sheathed _Arundo Phragmites_; and the round shoots of _Digraphis_, its split sheath and firm leaves, suffice to distinguish it. _Molinia_ also has a tuft of hairs instead of a ligule, and a split sheath, and its habit is different. _Alopecurus geniculatus_, with its “kneed” shoots, has a totally different habit from _Glyceria_, and its very high ridges and want of visible air-chambers complete the diagnosis. _Catabrosa_ is a small creeping aquatic with very flaccid leaves, quite glabrous and soft. Also sweet-tasting. +B. Not aquatic, and devoid of visible air-chambers in leaf or sheath. Often perennial, i.e. having stolons or other branches with no rudiments of flowers in them, and with relics of old leaf-bases.+ (α) Sections of sheathed leaves acute: either two-edged or four-edged. (1) Section of sheathed leaves quadrangular. Blades of leaf thin and dry, sparsely hairy. Sheath quite entire. Woods and shady places. _Melica uniflora_, L. (Wood Melick). Lamina slightly tapered below, convolute. Ligule obsolete, with a stiff subulate process on the sheath opposite the blade-insertion. Ridges below, but not above. _Melica nutans_, L. (Mountain Melick). Ligule longer, and without the awl-shaped peg. Only in Scotland and W. of England. Both are shade grasses of no agricultural value. _M. uniflora_, with its quadrangular shoots and anti-ligular peg, cannot be confounded with any other grass. (2) Sections of sheathed leaves more or less acutely two-edged, owing to the keels of the compressed equitant leaves. (i) _Shoots broad and fan-like, much compressed, with old brown leaf-sheaths below, sometimes burst by the intra-vaginal branches: leaf ridgeless, with prominent keel. No underground stolons._ _Dactylis glomerata_, L. (Cock’s-foot). An early and quick-growing pasture-grass, which forms much aftermath. Grows on all soils. Often coarse. Coarse tussocks, and harsh, with broad thick succulent bluish-green leaves. Section of sheathed leaves acutely naviculate. Prominent obtuse ligule, torn above. Lamina long, rough, acute, with white lines if held up, and serrulate edges. No flanking lines[6]. No stolons (Fig. 6). There is a cultivated variety of _Dactylis_ with broad opaque white stripes down the leaves: these are totally different from the translucent white stripes seen on holding the wild form, or _Aira cæspitosa_, up to the light. Another cultivated “ribbon-grass”--_Digraphis_--has _round_ shoots, _split_ sheaths, and a different habit, and the same applies to its wild form. Probably the only serious chances of confusion with _Dactylis_ are between it and _Poa pratensis_, which also has flattened shoots and closed sheath; but in the latter the section of the shoot is _elliptical_--not _naviculate_,--the keel is far less prominent, and the ligule shorter. Moreover _P. pratensis_ is a creeping stoloniferous grass, less harsh, and with less pointed leaves. The distance to which the sheath is torn may be from 1/8 to 1/2 down. Leaves tend to remain conduplicate. Margins serrulate with teeth extremely short and directed forwards. (ii) _Shoots compressed but narrow: the section almost rhomboid with rounded edges._ _Poa trivialis_, L. (Rough-stalked Meadow-grass). Conspicuous in deep rich pastures and orchards, preferring slight shade and rich soil. Valuable pasture and hay grass. Rootstock shortly creeping, branches extra-vaginal and above ground, shoots rough. Blade narrow, harsh, with an acute point, thin, shining below, ridgeless, with flanking lines and keel. Ligule acute, and short or long (Fig. 8). _Sesleria cærulea_, Ard. (Blue Moor-grass), of our northern limestone hills, has narrow, flat, glaucous blue, stiff, mucronate leaves, with scabrid apex. Ligule ciliate. _Poa trivialis_ is most likely to be confounded with other Poas, especially _P. annua_ and _P. pratensis_, since they both have thin leaves and flat shoots; but _P. annua_ has a split sheath, less acute and duller leaves, is annual, and less harsh, and the shoot-section is flatter at the sides and rounder at the ends. _Poa pratensis_, L. is larger and more stoloniferous, with both extra- and intra-vaginal branches, culms erect and smooth, sheaths smooth, and the shoot-sections elliptical--not cornered or rhomboidal--and with darker green and larger, thicker, 7-veined, more glossy, and less harsh leaves, with shorter, blunter ligule. _Poa compressa_, L. also presents difficulties, but the sheath is split, and the ligule is shorter than in _P. trivialis_, the leaves thicker, and the shoot-sections more linear-oblong or elliptical. (β) Sections of sheathed leaves rounded, circular or oval, there being no prominent keels. (1) Section of sheathed leaves circular or nearly so, the shoots being only slightly compressed. * _Perennial._ _Bromus inermis_ (Awnless Brome). Sections circular, the leaves being convolute, base shelving. Glabrous sheaths and leaves. Stoloniferous. Ligule short, truncate, and finely toothed. A forage grass of the Hungarian steppes. Now being grown in this country, but of doubtful value here. _Bromus erectus_, Huds. (Upright Brome). A weed. Sections oval and rounded, but leaves equitant. Radical leaves remain folded and almost subulate, hairy edges. No stolons. Fields, &c. It is a weed on dry lands, and of little or no value. _Bromus asper_, Murr. (Hairy Brome). In thickets, &c.: a weed, and useless. Leaves green, long, flat, hanging, and eared. Sheath with scattered deflexed hairs. Lamina tapering at the base. Keel a white line, ridges inconspicuous: distance between veins 2-3 times breadth of latter. Ligule very short, toothed. _B. giganteus_, L. (Tall Brome), also comes here. It is less common and glabrous. Woods, &c., a useless weed. ** _Annual or biennial._ _Bromus mollis_ (_B. arvensis_, var. _mollis_, L.), Field Brome. A too abundant and useless weed in water-meadows and hay-fields. Softly downy. Blades very thin and not eared: dry. _Bromus sterilis_, L. (Barren Brome). A useless weed. Rough and downy, but less so than the last. Moist waysides, &c. The Bromes are extremely variable and difficult to determine by the leaves. The annual species are apt to be biennial or (_B. sterilis_) perennial; and some vary much as regards hairiness--e.g. _B. mollis_ is connected by a series of semi-glabrous forms to varieties quite smooth, all grouped by Bentham under _B. arvensis_. _Bromus asper_, being auriculate and a shade-species, runs some risk of confusion with _Hordeum sylvaticum_, but _Hordeum_ has a _split_ sheath and in _B. asper_ the translucent interspace between the ridges is 2-3 times as broad as in _Hordeum sylvaticum_. The other species of _Bromus_ are not eared, and their entire sheaths at once distinguish them from _Hordeum_. _Bromus giganteus_ has leaves glabrous and very like _Festuca elatior_. The red split sheaths of the latter, its sharp ears and prominent ridges afford the best distinctions; and _B. giganteus_ has broader leaves and more evident serrulation or descending bristles at the basal margins. (2) Section of sheathed leaves elliptical, owing to the shoots being compressed. Sheaths often only slightly split above. No hair on surface of leaves or sheaths. ✲ _Margins of leaves smooth and even. Blades without ridges, a keel and flanking lines, acute, base rounded. Ligule of lower leaves very short._ _Poa pratensis_, L. (Smooth-stalked Meadow-grass). An early and valuable dry pasture-grass, but though deep-rooted, it yields thin hay: its chief value is for “bottom grass” and in lawn mixtures, &c. Leaves stiff and pointed. Extra-vaginal rooting underground stolons, and intra-vaginal branches. Shoots smooth. Keel slight: seven principal veins and smaller ones between. Leaves blunter and broader than in _P. trivialis_. _Poa alpina_, L. (Alpine Poa). On mountains in the north. No stolons. 4-5 veins on each side of the median one. _Poa pratensis_ presents similar difficulties to _P. trivialis_: for diagnoses see p. 42. It is distinguished from _P. nemoralis_ by its closed sheath, thicker, blunter and harder leaves, linear-elliptical shoot-sections, and light coloured nodes, as well as by its habit. All other Poas have shallow and poorly developed roots. _P. fertilis_ is a form very like _P. nemoralis_, with rougher leaves and longer ligule, introduced into cultivation. ✲✲ _Margins of leaves scaberulous with descending hairs. Very low flat ridges. Sheath smooth._ _Briza media_, L. (Quaking Grass). A weed in meadows, indicating poor soil--e.g. moor-lands and chalk--but eaten by sheep. Tufted and slightly creeping perennial. Ligules very short, entire. _Briza minor_, L. (Lesser Quaking-grass). Annual. Leaves broader and shorter, and ligules longer. In the south and rarer. II. SHEATHS SPLIT, AT LEAST SOME DISTANCE DOWN. +A. Glabrous--i.e. with no obvious hairs[7].+ (_a_) Grasses with setaceous or bristle-like leaves;--i.e. the lamina of the lower leaves remains permanently folded instead of opening out flat. (1) Ligule obsolete, auricled at the junction of blade and sheath. _Festuca ovina_ (Sheep’s Fescue). Densely tufted perennial. Leaves hard, glabrous and often glaucous, with 5-7 ridges if forcibly unrolled, ears short, stiff and erect. Branches in permanent sheaths. Chiefly useful as pastures on downs and dry chalk-soils. Several varieties are recognised by agriculturists, as hard, red, various-leafed, fine-leafed Fescue, &c. (see Figs. 13 and 18). _Festuca Myurus_, L. (Rat’s-tail Fescue). Annual, longer auricles, and hair on the ribbed inrolled surface. A road-side weed. _Festuca ovina_ presents difficulties with its varieties and with _F. Myurus_, L. (var. _sciuroides_, Roth.). The chief varieties of _F. ovina_ are Hard Fescue (_F. duriuscula_, L.), taller and with some of the upper leaves flat, and found in moister and rich soils: Red Fescue (_F. sabulicola_, Duf. or _F. rubra_, L.) more or less creeping and with red sheaths to the lower leaves, on poor stony land--_F. heterophylla_ is a form of this on chalky soils, with flat leaves above: and _F. tenuifolia_ a very wiry form on sheep-lands. They all pass into one another, however, and cannot be distinguished by the leaves (see Figs. 18-20). _F. Myurus_ (var. _sciuroides_) is ruderal and annual, and has longer hairs on the ridges of the folded leaves. It has no agricultural value. (2) Ligule membranous, not auricled. (α) _Bristle-like (setaceous) leaves, very hard and stiff, and more or less solid._ _Nardus stricta_, L. (Moor Mat-grass). Roots very tough and stringy: ligule small, but thick and blunt. Leaves channelled: upper erect, lower horizontal. Sheath smooth. Moors and sandy heaths: useless (Figs. 2 and 26). _Aira flexuosa_, L. (Wavy Hair-grass). Roots fibrous. Leaves short, filiform, terete, solid--the channel hardly discernible. Ligule short, obtuse. Heaths, &c. Of little use, even for sheep (Fig. 28). (β) _Leaves bristle-like, but distinctly due to inrolling of edges._ _Aira caryophyllea_, L. (Silvery Hair-grass), is scabrid. A weed, with very slight foliage. _A. præcox_, L. (Early Hair-grass). Greener and more glabrous. Habit more rigid. _A. canescens_, L. (Grey Hair-grass). Glaucous or purplish; rare, on S.E. coasts. (γ) _Leaves narrow and more or less involute, and subulate upwards, but easily unrolled, and apt to become flatter as they age._ _Avena pratensis_, L. (Perennial Oat). Leaves rather thin, dry, harsh, ridgeless, with flanking lines and a keel[8]; glaucous, glabrous, but edges scabrous. Usually involute, but may open out. Ligule long ovate-acute. Dry pastures, especially on calcareous soil, and of little value. _Poa maritima_, Huds. (Sea-grass). Leaves narrow, rather short, and U-shaped in section. Involute: ridgeless, with flanking lines, but no keel; soft and rather thick. Ligule rather long, obtuse and decurrent. Useless agriculturally. For difficulties with other species of _Avena_ and _Poa_ see pp. 44, 54 and 60. (_b_) Grasses with the leaves expanded, more or less flat. (1) Blades conspicuously ridged--i.e. the surface is raised in prominent longitudinal ridges with furrows between. (i) _Leaves rigid and hard, sharp pointed. Sheath and outer leaf-surface usually glabrous._ _Aira cæspitosa_, L. (Tufted Hair-grass). Forms large tufts. A coarse weed forming bad tussocks in wet meadows and pastures: useless for fodder. Leaves flat. Ligule long, acute. Ridges equal, high and sharp, and scabrid, with 5-6 white lines between, if viewed by transmitted light. Wet meadows. _A. cæspitosa_ cannot easily be mistaken for any other species. _Alopecurus geniculatus_ is also a moisture-loving grass with strongly ridged leaves, but the interspaces are far less translucent and the whole habit is different. All the other species of _Aira_ have involute and setaceous leaves, and even _A. cæspitosa_ is apt to roll in its leaves in mountain varieties, but they are easily flattened out, and show the ridges. _Psamma arenaria_, Beauv. (Sea Mat-grass). This is one of the most valuable “sand-binders,” its long matted rhizomes holding loose sand together. It is a sea-shore grass, of no use for fodder. It was formerly much used for mats and thatching. Leaves concave, long, narrow, erect, scabrid and glaucous above, and polished below: pungent. Ridges rounded, alternately high and low. Sheath long. Ligule very long and bifid. _Elymus arenarius_, L. (Sand Lyme-grass). Like _Psamma_, this is a “sand-binder” and of no use for fodder. Leaves concave, and eared at the base of the blade: ears pointed and tend to cross in front. Ligule very short and obtuse. Ridges flattened above, not scabrid. Apex of blade rolled, forming a hard spine. _Psamma_ cannot easily be mistaken for the much less common _Elymus_, as it is not eared, and the ridges and ligule are very different. (ii) _Leaves not specially rigid and hard, and often thin; glabrous, or shining below. Ridges less evident._ * _Ligule very short or obsolete; blade firm but not hard, glabrous or nearly so, and shining below. Sheath often coloured red or yellow at the base._ † _Sections of sheathed leaves narrow, oblong, owing to compression of shoots. Sheath nearly entire._ _Lolium perenne_, L. (Perennial Rye-grass). Very valuable pasture-grass, especially on clay. Less successful as hay. Deep rooted tufts. Glossy dark green. Ligule short (Fig. 11). Sheath red or purplish below. Blade conduplicate and keeled, often rounded, collared or eared at the base; with rounded ridges and rough above, shining below. When the ears are well developed their points often cross one over the other in front of the sheath. _L. italicum_, Braun. (Italian Rye-grass), is an earlier and better variety for hay and sewage farms. Shoot more rounded in section, and has less marked veins on the more rolled leaf. _L. temulentum_, L. (Common Darnel), is annual and a weed of corn-fields. Foliage usually rougher. _Lolium perenne_ presents some difficulties in relation to such forms as _L. italicum_, species of _Agrostis_ and _Festuca_, _Alopecurus pratensis_, _Cynosurus_ and _Agropyrum_. Owing to the leaves not being always strictly conduplicate in the first year, the flat shoots may not sharply mark it off from _L. italicum_. Its somewhat looser, almost stoloniferous tufts, and darker green foliage, less polished below and usually narrower and harder, have then to be taken into account. The ridges of _Lolium_ are often like those of _Festuca pratensis_; and the shining lower surface and rather firm leaves and red sheaths, present other points of confusion. The smooth basal margins of _Lolium_, absence of white translucent lines when held up, and the different ligule and ears afford distinctions--the ligule of _Festuca_ being a mere line, and the ears pointed and projecting, whereas they may be mere lateral ledges in _Lolium_. _Cynosurus_ has the ligule and ears very like those of _Lolium_, the ears being mere ledges; but the former has yellow sheaths, firmer and thicker leaves with more evident ridges, and the old plants usually have the characteristic crested spikes remaining. _Cynosurus_, moreover, has the sheath split only a short way down. With regard to _Agrostis_, there is no colour in the sheath, the ligule is longer and pointed, and the leaves drier and thinner than in _Lolium_, and harsher on both surfaces. _Agrostis_ has also no ears. _Alopecurus pratensis_ has much broader and flatter ridges than _Lolium_ and a longer ligule, and its sheaths are dark-brown or black--not red; but _A. agrestis_ has very similar ridges to _Lolium_ and may easily be confounded at first. _Agropyrum_ is sometimes nearly glabrous, and may then be confused with _Lolium_ by beginners: its low ridges, curled and pointed ears, obsolete ligule, and thinner, drier, harsher blade, as well as the stolons, distinguish it. _Lolium temulentum_ and _Hordeum murinum_ occasionally cause difficulty, but the latter is always more or less hairy, its blades thinner and drier, and the ridges less raised. †† _Sections rounded--elliptical or nearly circular. Sheath distinctly split, at least above._ _Cynosurus cristatus_, L. (Crested Dog’s-tail). Useful as pasture on dry soils, but only moderately so as hay. Blade narrow, slightly eared or collared below, tapered above; firmer than _Lolium_. Sheath only split a short way down. Yellow or yellowish-white at the base. Leaves conduplicate or convolute, short and narrow, the ligule short: minute ears at base. Usually easily recognised by the withered culms and persistent pectinate spikes (Fig. 16). _Festuca elatior_, L. (Meadow Fescue). A valuable meadow and pasture grass, though somewhat coarse. Several varieties are known. Best on heavy soils. Deep rooted. Blade flat and broad, conduplicate, sharp-eared at the base, and there rough at the margin: lower surface polished. Rich green. Mid-rib flat above, numerous ribs with white lines between if held up and examined with a lens. Ligule obsolete (Figs. 12 and 17). _Arundo Phragmites_, L. (Common Reed). A large aquatic, reed-like creeping grass, with broad leaves (3/4 to 1 in.), flat, rather rigid, acuminate, glaucous below, hispid at edges. Sheath smooth, striate, bearded at mouth. Ligule a mere fringe of hair. (Cf. _Digraphis_, p. 54.) _Cynosurus_ is not very liable to confusion; but it has resemblances to _Lolium_ (see p. 49) and to species of _Agrostis_. The leaves of _Cynosurus_ are firmer, thicker, less dry, and with a shining undersurface, and the sheath is only split above, and yellow below; whereas _Agrostis_ has relatively thin and dry leaves, rough surfaces and margin, distinct ridges, and converging margins as the blade nears the sheath. _Festuca elatior_ is easily confused with the glabrous Bromes. For _B. giganteus_ see p. 43. _Bromus erectus_ is distinguished by the entire sheath, usually hairy, the want of auricles, and the conduplicate--not convolute--leaves. _Agrostis_ has thinner, duller, and drier leaves, and no red sheath. _Alopecurus pratensis_ has more depressed, flatter and broader ridges than _Festuca_, and a longer ligule, and lacks the pointed ears. ** _Ligule whitish, membranous, long, or at least well developed. Sheaths not coloured or brown. Leaves thin and rough, at least at the base. Ridges not very prominent, but numerous and distinct._ _Agrostis stolonifera_, L. (Fiorin). Stolons, with numerous short offsets bursting through the leaf-sheaths. Blade flat, rough, tapering, with rounded ridges, and convolute in bud: there are no auricles, but the blade may narrow, and form ledges, as it runs into the sheath. Sheaths nearly smooth. Ligule long and pointed, and often toothed at the margins. The leaves vary in breadth. This and _A. vulgaris_, With. with shorter ligules, and, possibly, _A. canina_, L. with finer leaves, are varieties of _A. alba_, L. Only the variety _A. stolonifera_ is of moderate value for pasture, especially on poor soils, as it lasts late into autumn: the others are weeds, like couch-grass. _Agrostis_ is full of difficulties for the beginner. The weed-forms often spring up after wheat has been cut, and count as “twitch,” like _Agropyrum_. All the ordinary forms--_A. stolonifera_, _A. vulgaris_, and _A. canina_--may be included in _A. alba_ (Linn.). On dry hills a close tufted grass, with setaceous leaves, and in rich soils creeping and luxuriant with broad leaves. It is one of the few grasses that thrive in wet soils. The chief points in the flat-leafed forms are the thin, dry leaves, rough on both sides and on the margins, with distinct raised ridges, and the base of the leaf narrowing suddenly into its insertion with the sheath, with no auricle, but with a long membranous ligule. The sheath not coloured, and the blade convolute. Again, _A. stolonifera_ has a long, serrated, acute ligule, while _A. vulgaris_ has a much shorter, entire and truncate one, and narrower leaves. _Agropyrum_ is the grass most likely to lead to confusion. Its ears, lower ridges, very short or obsolete ligule, and pubescence (sometimes glabrous) distinguish it. _Cynosurus_ sometimes gives trouble (see p. 50) with _Alopecurus pratensis_: the sheaths, ligule and flattened ridges should suffice for distinction. _Alopecurus geniculatus_ is even more like _Agrostis_, but its ridges are more prominent and sharp, and its aquatic habit and bent “knees” distinguish it. _Alopecurus agrestis_, in dry corn-fields, has a thickened ligule, sometimes coloured, and is annual or biennial, but otherwise very like _Agrostis_. _Alopecurus pratensis_, L. (Meadow Foxtail). Large grass with stolons; very early, and much prized as pasture and hay, but soon dies out on light poor soils. Especially good for stiff soils. Sheaths long, ridged, brown or nearly black at the base as they age. Ligule distinct and obtuse, entire. Leaves numerous. Blades long, dark green, succulent and scabrous: ridges numerous and flat above, but distinct (Fig. 9). _A. agrestis_, L. in S. England has shorter leaves, and ridges not flattened; it is a troublesome pest of arable land, but does not usually invade pasture. _A. geniculatus_, L. is semi-aquatic, and like the last. It is easily recognised by its sharply bent “knees,” and is of little value (Fig. 3). _Alopecurus_ shows resemblances to _Lolium_ (see p. 49), _Festuca_ (see p. 50), and _Agrostis_ (see p. 52). If well grown its ridged sheath and leaves, the former brown or black at the base, aid in distinguishing it. (2) Blades either devoid of ridges or with very inconspicuous ones. * _No trace of ridges, and the mid-ribs not prominent, but the leaves show median lines flanked by finer ones when held up. Blades thin and narrow. Somewhat keeled._ (i) _Shoots compressed._ _Poa compressa_, L. (Flat-stemmed Meadow-grass). Leaves rather short, more or less glabrous or glaucous, and +V+-shaped at the base; shoots compressed, and naviculate in section. Ligule short and thin. Sheath tends to be closed below. A creeping perennial on commons and waste lands, and of little or no value. _Poa annua_, L. (Annual Meadow-grass). Small annual. Compressed shoots, limp. Leaves linear, pale, sub-acute, thin, often wavy, flat, flaccid, bright green; dull or slightly shining and +V+-shaped in section below. Ligule long, pointed, whitish and clasping the shoot. It is a harmless weed, and since it puts out shoots all the year round, furnishes a certain amount of pasturage. (ii) _Shoots terete or nearly so._ _Poa nemoralis_, L. (Wood Poa). Leaves and sheaths smooth. Blade bright green, thin, often glaucous, linear-narrow, flaccid, acute. Ligule almost obsolete. Section of shoots round. Of little value. _Poa bulbosa_, L. (Bulbous Meadow-grass). Stems bulbous at the base. Ligule long and acute. Leaves very narrow and tapering. Sections of shoot round. Coasts of S. and E. All the Poas, except the aquatic ones (_Glyceria_) and _P. maritima_, have glabrous ribless blades with the median lines, and slight keel. _P. pratensis_, _P. alpina_ and _P. trivialis_ (Fig. 8) have entire sheaths (as have _Glyceria fluitans_, _G. aquatica_ and _P. maritima_), but the others have them split some way down. The leaves of _P. pratensis_ and _P. compressa_ are firmer than the thin leaves of _P. annua_, _P. trivialis_ and _P. nemoralis_. Sheaths flattened in _P. pratensis_, _P. compressa_, _P. annua_, and _P. trivialis_; but rounded in _P. nemoralis_. _Glyceria aquatica_ and _G. fluitans_ have netted sheaths. _Poa annua_ is annual, and _P. bulbosa_ has the bulbous base. _P. maritima_ has involute leaves and no keel, and the rare _P. alpina_ has short rigid keeled mucronate leaves, with tip often inflexed and thickened scabrid edges. The leaves of Avena are apt to appear similar to those of the Poas at first sight, but the former are hairy, and ridged, dry as well as thin, and the peculiar median lines of _Poa_ are wanting. _Poa bulbosa_ has drier leaves than usual, but its leaves are devoid of ridges. ** _Ridges can be detected, but are slight and not distinct. Margins scabrid, at least at the base._ † _Leaves firm, flat, linear, acuminate, not narrowed below. Glabrous. Ligule membranous._ _Digraphis arundinacea_, Trin. (Reed-grass). Sheathed leaves round in section; blades convolute, tapering above, flat, firm, long and broad (1 in.) below. Mid-rib and veins numerous, and prominent below. Stoloniferous: branches extra-vaginal, often with deep red basal scales. Sheaths with much overlapping membranous margins, with a collar-like ledge above. Ligule long and somewhat acute. Wet ditches, &c., of no value (Figs. 7, 14). For distinction between _Digraphis_ and _Dactylis_ see p. 41. _Poa pratensis_ is at once distinguished by its flattened shoots, more rounded leaf apex and shorter ligule. _Arundo Phragmites_ is easily distinguished by the ligule (see p. 51), and the other aquatic grasses are quite different (see p. 39). _Phleum pratense_, L. (Timothy-grass). No stolons, but bulbous on dry ground. Early, and a heavy cropping hay grass: also excellent pasture; branches intra-vaginal, but burst the glabrous sheaths. Old sheaths fibrous. Leaves short, convolute, with scabrid margins owing to deflexed teeth: ridges obsolete above, no keel; broader and greyer green than _Alopecurus_. Ligule short on radical leaves, thin. Pastures. Perennial. The smooth ligule, deflexed marginal teeth, and no keel distinguish it from _Arrhenatherum_. _Phleum arenarium_, L. (Sand Phleum). Shoot annual, with no bulbs. Leaves broad, flat and glabrous, but rough at the edges, with descending teeth. Ridges low and flat. Sheaths smooth: leaves conduplicate. Ligule long. Sandy coasts, &c. A weed. _Phleum asperum_, Jacq. and P. _Bœhmeri_, Schrad. are rare ruderal plants, and _P. alpinum_, L. is confined to the Scotch Highlands. _P. arenarium_ is sharply distinct by its conduplicate leaves and habitat. _Alopecurus pratensis_ has narrower and less grey-green leaves than _Phleum pratense_, its ligule is shorter and blunter, its sheath more grooved and dark below, and the ridges more distinct and flat. It is relatively well rooted and is stoloniferous. _Arrhenatherum avenaceum_, Beauv. (False Oat-grass). Loose tufts with short stolons, or bulbous below. Leaves few, narrow, thin, dry, rough, with very low flat ribs, convolute in bud, and practically glabrous. Sheath smooth. Ligule truncate, hairy on its outer surface. Bitter, and commonly undervalued by agriculturists, but useful in mixed pasture, and yields bulky, coarse hay. There are often a few sparse isolated hairs on the low ribs. The base enters the sheath with slight and sometimes pinkish ledges. Ridges hardly observable. Traces of roughness if rubbed downwards. White lines, about 5 each side on holding up to the light. The not very long leaves taper slightly below. _Arrhenatherum_ is liable to confusion with _Holcus_, _Anthoxanthum_, _Molinia_ and _Avena_, but it is typically glabrous, whereas the others are hairy. From _Holcus_ it is easily distinguished by the sheaths, ligule and soft hairs of that genus. _Anthoxanthum_ differs in its habit, ears, scent, sheath and ligule. _Molinia_ differs in habit, ligule, sheath, and tough stringy roots, and the shape of the leaves. _Avena pratensis_ differs in its narrow leaves, less prominent ridges, and ligule; _A. flavescens_ in its much broader and coarser hairy leaves, and the ligule; and _A. pubescens_ in pubescence and flat-shoots and ligule. †† _Leaves very thin, blade tapering below. Keel prominent, but no ridges above. Ligule long and torn._ _Milium effusum_, L. (Spreading Millet-grass). Tufted perennial. Leaves linear-lanceolate, scabrid above. Sheath smooth. Bitter tasting. May be slightly hairy. Woods. It is much liked by birds, but is of no value in agriculture. +B. Leaves or sheaths, or both, distinctly hairy.+ (α) Leaf-blades eared at the base. (_a_) Ears sharply pointed. Leaves convolute, and sections of shoots round. Ligule short and inconspicuous. _Agropyrum repens_, Beauv. (Couch-grass). A troublesome weed of arable land and gardens, &c., owing to the extraordinary vitality of its underground stolons. The young shoots are readily eaten by stock. Perennial, and extensively stoloniferous; bright or glaucous green. Blade thin, dry, rough edged, hairy and rough above, glabrous or hairy below. The short ligule fringed. Ears long, or sometimes short, pointed; often obliquely crossing in front of the sheath. Ridges inconspicuous. Hairs may be absent from the sheath, and nearly so from the blade. The sea-shore varieties are stiffer and more glaucous, the leaves more ribbed, involute and pointed--e.g. _A. junceum_, Beauv. _Agropyrum caninum_, Beauv. (Bearded Wheat-grass). Tufted weed, not creeping, in woods, &c. Blade thinner and rougher beneath, but very variable. Properties similar to those of _A. repens._ _Agropyrum_ may be confused with _Lolium_ (see p. 49) and _Agrostis_ (see p. 51), but hardly with any other grass, and with these only because it is liable to be glabrous or nearly so on poor soil. _Elymus_ has much more pronounced ridges than the sea-shore varieties of _Agropyrum_. (_b_) Base of blade with inconspicuous rounded ears. Leaves convolute. Ligule conspicuous. _Anthoxanthum odoratum_, L. (Sweet Vernal-grass). Compact tuft. Common in pastures and hay, but it only forms a small proportion of the crop. One of the earliest grasses, and the principal one, which gives the scent to new-mown hay: a perfume has been extracted from it. Its value as fodder is probably overrated. Bitter tasted. Leaves more or less hairy at margins, especially at throat of sheath, flat, and slightly ridged. Sheath furrowed, often pubescent. Ligule long and blunt, with ciliate margins. Sweet scented when dried. The most shallow rooted of all meadow-grasses. Leaves often short and few. _Anthoxanthum_ is sometimes confused with _Arrhenatherum_ (see p. 56) and _Molinia_; the latter differs in its ligule--a tuft of hair--its stringy roots, tapering leaf-base, less obvious ridges, and smooth sheaths, &c. _Anthoxanthum_ is deep green and often very luxurious in rich wet soils--e.g. in Devonshire. (_c_) Ears as mere collar-like ledges where the blade joins the sheath. Sheath usually pubescent or hispid with reflexed hairs. Ridges inconspicuous. Ligule very short. ✲ _Perennial, with firmer leaves_. _Hordeum sylvaticum_, Huds. (Wood Barley). Leaves flat, thin but firm, rather broad, scaberulous. Sheath hispid, with reflexed hairs. Blade not tapering below. Translucent spaces between the veins as broad as the latter. Ligule short and blunt. Shady places. Useless. _Hordeum pratense_, Huds. (Meadow Barley). Tufted, or bulbous below. Leaves narrower, flat, tending to roll up, scabrid above and hairy beneath. Sheath narrow, hairy. Moist meadows, and of some use as pasture in the young state. ✲✲ _Annual, with thin dry leaves_. _Hordeum murinum_, L. (Wall Barley). Coarse tufts; leaves small, narrow, hairy or scabrid. Sheaths sparsely hispid, or very downy, inflated. Roads, &c. A useless weed. _H. maritimum_, With. is a sea-side form, smaller and more glaucous. Sheaths hairy. (β) Leaf-blades not eared at the base. * Sheaths of radical leaves veined with red-purple. _Holcus lanatus_, L. (Yorkshire Fog). A useless weed, but very common in pasture and hay; forming tussocks, greyish-green, softly hairy (tomentose). Blades with roundish ridges. Ligule short and obtuse. Sheath somewhat keeled, with trace of collar ledge. It is said to have a bitter taste (Fig. 15). Ligule pilose. Tufted hairs along the broad rounded ridges, and on the lower surface and prominent keel. The much rarer _H. mollis_, L. is not so long-haired, except on the nodes, and is more creeping and slender in habit. It is a “twitch.” The Hordeums present several points of difficulty to beginners. The differences between the species are given above. _H. maritimum_ has narrower and thicker leaves than the rest. Bromes are most likely to be confounded with Hordeums, but they have entire sheaths and no ears (see p. 43). For distinctions between _H. murinum_ and _Lolium_ see p. 49. _H. sylvaticum_ and _Bromus asper_ (p. 44). ** No conspicuously red-veined sheaths. † Ligule absent, or a tuft of hairs. _Molinia cærulea_, Mœnch. (Purple Molinia). Tussocks, with tough stringy roots. Leaves narrowed below, and tapering above to a long point, ridges obsolete; very thin and dry but fairly stiff, and hairy above, especially at the base. Ligule absent, or a tuft of hairs. Sheaths smooth. Moors. Useless as forage, but used locally for brooms. _Molinia_ is not easily confounded with any others but _Anthoxanthum_ (see p. 57), _Arrhenatherum_ (see p. 56) or _Brachypodium_. _Brachypodium sylvaticum_ is distinguished by habitat, its broad leaves, membranous ligule, fibrous roots, &c. _Kœleria cristata_, Pers. (Crested Kœleria). Very short, perennial in dry pastures, pubescent, pale green. Leaves narrow, tapering below, soon involute, ciliated. Ridges prominent, alternately high and low. Ligule obsolete, or a mere jagged yellowish line. Useless. _Triodia decumbens_, Beauv. (Decumbent Heath-grass). Low perennial. Leaves narrow, obtuse, slightly ridged, tough, at length involute, with long, soft hairs, especially below and on the edges. Sheath grooved, hairy, especially at the throat. Ligule a tuft of hairs. Section of shoot flat; leaves conduplicate. Of no known use as fodder. The rare grasses _Panicum glabrum_, Gaud., _P. viride_, _L._ and _P. Crus-galli_, L. introduced in the S.E. counties also come here. †† _Ligule membranous._ _Avena flavescens_, L. (Yellow Oat-grass). Loose tufted perennial, pale green, with rounded shoots bursting the sheaths. Leaves flat, slender, soft, fine-ribbed and hairy, especially on the low ridges above. Sheath hairy, especially below, not keeled. Ligule short, obtuse, often truncate, ciliate. A valuable pasture and meadow-grass, also in water-meadows. Its roots are abundant, and it will grow well in calcareous soils (see Fig. 10). _Avena pubescens_, Huds. (Downy Oat-grass). A variety of _A. pratensis_ (see p. 47), but less densely tufted, and the leaves flat and pubescent, and especially the sheaths very pubescent. Ligule ovate-acute. Shoots flat. Dry districts, and a weed. _Avena flavescens_ is not easily confounded with any other grass if well grown. All the Poas otherwise like it are glabrous, and without the ridges. The same applies to _A. pubescens_. _Arrhenatherum_ is also glabrous, its leaves narrower, its ridges much flatter and broader, and its ligule is hairy outside (see p. 56). _Brachypodium sylvaticum_, Beauv. (Wood False-brome). Rather slender, perennial. Leaves flat and devoid of ridges; long, very thin and dry, limp, slightly tapering below, hirsute. Sheath round, hairy. Ligule fairly long, obtuse, toothed. Copses, &c. Useless. _Brachypodium pinnatum_, L. (Heath False-brome), is a species growing in the open, with narrow, firm, rigid, erect leaves, hardly hairy; with distinct ridges, and tending to roll up. Ligule fringed with hair. Open heaths. Useless. The only grasses likely to be confounded here are the Bromes, and they have entire sheaths. CHAPTER IV. ANATOMY AND HISTOLOGY. The principal anatomical features observed in the leaves of grasses--apart from finer histological details into which it is not my purpose to enter--concern the characters of the epidermis and distribution of the stomata and hairs, the arrangement of the chlorophyll-tissue, that of the mechanical tissue (sclerenchyma) and the vascular bundles to which the venation and ribbing of the leaves are due, and the presence or absence of those peculiar thin-walled cells (motor-cells) which bring about the infolding or inrolling of the lamina (see p. 25) as they lose water, and, finally, the presence or absence of conspicuous lacunæ or air-spaces so characteristic of aquatic species. Several observers have occupied themselves with these matters, and the researches of Schwendener, Duval Jouve, Pfitzer, Pée-Laby, and others have rendered it possible to group most of our grasses according to the microscopic characters of the leaves, somewhat as I have done in Chapter V. Reference has been made to the rolling and folding of leaves, due to the thin-walled cells on the upper surfaces capable of varying in turgescence (motor-cells). These are specially adapted epidermal cells found on the upper surfaces only. In the leaves of _Poa compressa_, _P. annua_ (Fig. 21), _P. nemoralis_, _P. alpina_, _Catabrosa_, _Sesleria_, &c., a row of these motor-cells, easily distinguished by their large size, thin walls and clear contents, is found on each side of the mid-rib; as they dry the leaf folds its two halves together (conduplicate), and on the re-absorption of water they flatten the two halves out again. In _Dactylis_ these flanking rows coalesce into one over the mid-rib. In other leaves, e.g. _Avena pratensis_, _Festuca elatior_ (Figs. 17, 22), _Melica_, _Elymus_ (Fig. 25), &c., there are in addition to these two flanking rows, other sets of motor-cells between the other ribs, and their combined action causes the halves of the lamina to inroll, usually one-half inside the other--convolute. [Illustration: Fig. 21. Transverse section of left-half of leaf of _Poa annua_ (× about 50) showing keel below, and two flanking lines of motor-cells (slightly shaded) above the median vascular bundle of the mid-rib. Hence the leaf folds. The half lamina has six smaller vascular bundles, only the stronger one girdered. Ridges practically obsolete and subtending bands of sclerenchyma slight: hence the leaf-surfaces are parallel.] It is easy to observe leaves of such grasses as _Festuca pratensis_ (Fig. 22), _Aira cæspitosa_ (Fig. 23), &c., which are wide open in the dewy mornings in summer, close up as the air gets dry and hot; and any such leaf may be seen to roll up after plucking and can be reopened by moistening it. [Illustration: Fig. 22. Transverse section of left-half of leaf of _Festuca elatior_, var. _pratensis_ (× about 50). The ridges are well marked and flattened above. The vascular bundles of two orders are girdered below, but only slightly above. There is no keel. There are well marked motor-cells--not shown in the figure--in each groove.] The epidermis of grasses has been closely investigated by Grob, but unfortunately his results concern very few of our native species. The principal elements are ordinary elongated cells, with plane or sinuous walls, various kinds of short cells intercalated between the ends of these, several forms of papillæ, hairs, &c. and stomata. The epidermis over the parenchyma of _Digraphis arundinacea_ consists of rectangular cells with plane walls. Series or bands of long cells only may alternate with other series where short cells intervene between the long ones--e.g. _Nardus_. _Nardus_ has some of the bands devoid of stomata, but abounding in short cells, whereas others (above) have stomata throughout. In _Nardus stricta_, _Glyceria fluitans_, _Sesleria_, &c., there are two kinds of short cells, some siliceous, others cutinized only. _Nardus_ has closely appressed small 2-celled hairs bent at right-angles, and some epidermal and parenchyma cells--especially below the stomata--have solid masses of silica filling the lumina. [Illustration: Fig. 23. Part of transverse section of leaf of _Aira cæspitosa_ (× about 30). Ridges very high and acute, each tipped with sclerenchyma, and containing an isolated vascular bundle--sometimes one or more small ones also. Motor-cells well developed at the base of each groove. The bundles are not girdered, but numerous bands of sclerenchyma almost join into a continuous band below. The leaf rolls inwards.] Short cells occur in _Holcus lanatus_, _Hierochloe borealis_ and _Dactylis glomerata_ interspersed between plane-walled cells. They may be silicified and vary in shape--square, saddle-shaped, elliptical, irregular, &c.; or they may be replaced here and there by asperities--e.g. _Elymus_--or in rarer cases by stomata. Grob has attempted the classification of their distribution in different grasses, but the subject is too complex for treatment here. The epidermis of many grasses is studded with short two-celled hairs bent sharply at right-angles; so that the pointed or blunt, hollow or solid, apical portion is appressed to the surface. Grob says that these are absent from the Hordeæ, whereas 90% of the Panicoideæ and many species of all other groups have them. Examples of the sharply pointed form occur in _Nardus_, of blunt ones in _Cynodon_ &c. In _Nardus_ they occur on the leaf surface both between and above the veins, but in _Hierochloe_ &c. they are confined to the margins. The following grasses have no hairs of either type: _Agrostis vulgaris_, _Calamagrostis lanceolata_, _Avena pratensis_, _Arrhenatherum avenaceum_, _Dactylis glomerata_, _Briza media_, _Arundo Phragmites_, _Glyceria fluitans_. The sharp, hard prickle-hairs which give the pronounced roughness to many leaves of grasses are longer than the foregoing, and stand off more from the leaf. They occur both on the surface and at the margins, and may be isolated--e.g. _Avena pratensis_,--or mixed with the short cells--_Aira canescens_, _Elymus arenarius_. They are very abundant on _Kœleria cristata_. _Leersia oryzoides_ has asperities at the margin of the leaf with their points directed upwards on the upper part of the leaf, downwards on the basal parts, and the direction of such minute marginal asperities often affords a useful distinctive character--e.g. _Phleum_, _Arrhenatherum_. The marginal asperities in _Nardus_ are siliceous. [Illustration: Fig. 24. Transverse section of part of leaf of _Agropyrum junceum_ (× about 40) partly inrolled; showing unequal ridges. The principal vascular bundles are girdered below, the sclerenchyma joining into a strong continuous sheath. Each ridge is tipped with sclerenchyma, and each groove has motor-cells--not shown in the figure--below.] Bristles--i.e. long, sharp, stiff hairs--are not very common. They occur on _Nardus_, _Anthoxanthum Puelii_, _Panicum_, _Cynodon_. Papillæ occur on the leaves of _Glyceria_, _Nardus_, _Leersia_, &c. _Poa pratensis_ has soft hairs on the upper epidermis. The stomata of _Sesleria cærulea_ are depressed and six-celled, two guard-cells being overgrown by four accessory cells, but in most grasses they are of the ordinary type with two elongated guard-cells only. [Illustration: Fig. 25. Transverse section of part of leaf of _Elymus arenarius_, partly inrolled (× about 30), showing ridges of unequal height, of which the higher are flat above. Vascular bundles girdered, the stronger above and below. Motor-cells in each groove cause the inrolling of the lamina by their contraction.] As regards the vascular bundles constituting the venation, they are as is well known parallel from base to apex in our common grasses, with linear leaves, and are usually of four orders as regards strength. Those of the first (e.g. mid-rib) and second orders have conspicuous vessels, but those of the third and fourth orders may be practically devoid of vessels, though xylem and phloem elements are always present. Contrary to the general assumption, there are frequent though minute transverse bundles joining the parallel veins. The rule is that one vascular bundle runs up each mid-rib or ridge, but exceptions occur--e.g. in _Arundo_ several bundles run up the mid-rib, and in _Aira cæspitosa_ (Fig. 23) and others even the strong ribs may have two or three bundles. Each vascular bundle has its own sclerenchyma sheath, and very often the stronger veins are accentuated owing to the vascular bundle having a girder-like band of sclerenchyma running conjointly with its sheath and joining the latter above and below--or below only--to the epidermis (Figs. 24 and 25). In many cases these lower girders spread out laterally below--fan-shaped in section--and nearly join the neighbouring girders. In other cases the strands of sclerenchymatous supporting tissue do not join the bundles, but run parallel to them, above or below, as separate strands just beneath the epidermis. Finally, these strands may separate from the bundles, and fuse below into a continuous layer under the epidermis; this occurs especially in leaves of xerophytes where the cuticle is well developed--e.g. in varieties of _Festuca ovina_ (Fig. 18), _Aira flexuosa_ (Fig. 28). The distribution of the strands of isolated sclerenchyma affords good characters. While there are none in _Mibora_, we find one large strand at the ridge of the keel and one at each margin, in addition to smaller ones subtending each vascular bundle, in _Avena pubescens_, _Sesleria_, _Poa annua_ (Fig. 21), _P. bulbosa_, _P. compressa_ and _Dactylis glomerata_. In _Festuca ovina_, _F. rubra_, _F. heterophylla_ (Figs. 18, 27) there are groups more or less pronounced at the keel and margins, or even a continuous band below, but none above the bundles. [Illustration: Fig. 26. Transverse section of leaf of _Nardus stricta_ (× about 50). The upper surface is represented by the four grooves and five ridges, each of the former with traces of motor-cells at its base. The deep shaded portions are sclerenchyma, strong girders of which join the vascular bundle of each ridge to the lower surface. This type is obviously derived from that in Fig. 19, and may be regarded as a permanently rolled leaf.] [Illustration: Fig. 27. Transverse section of leaf of _Festuca ovina_, var. _duriuscula_ (× about 50), the type of a permanently folded leaf. Seven ridges and six intervening grooves are seen: each of the latter with traces of motor-cells below. In each ridge is an isolated vascular bundle, and a narrow sclerenchyma band below.] Many grasses have an isolated band above and below each primary bundle only--e.g. _Panicum_, _Cynodon_--or above and below each of the other bundles as well--e.g. _Spartina_, _Arundo_, _Polypogon_, _Agrostis alba_, _Aira cæspitosa_ (Fig. 23), _Holcus lanatus_, _Glyceria aquatica_, _G. fluitans_, _Digraphis_, _Elymus_ (Fig. 25), _Agropyrum_ (Fig. 24), _Brachypodium_, _Nardus_ (Fig. 26). In _Psamma arenaria_ the lower bands join into a continuous layer. In the following there is a band like a girder above and below each bundle, and contiguous with it, joining it to the epidermis above and below--_Leersia_, _Phleum pratense_, _Calamagrostis Epigeios_, _Bromus erectus_, &c. Güntz points out that xerophilous grasses are apt to have upright, narrow (Figs. 26-28), grooved or folded leaves, with strong cuticle, and marked motor-cells when the leaves open. It is in grasses of this kind, especially such as inhabit dry sandy districts, that the subulate, solid or grooved leaves shown in Figures 18, 19 occur--e.g. _Festuca ovina_ and its varieties, _Aira flexuosa_, _Nardus stricta_, &c. The epidermal cell-walls are sinuous, the stomata protected--e.g. on the flanks of ribs and in grooves--and waxy or hairy coverings occur. Colourless water-storing cells are apt to occur between or around the vascular bundles, and the chlorophyll-tissues tend to be dense and well protected inside the leaf: strongly developed bast-sclerenchyma is also frequent (Fig. 18). In shade-grasses, on the other hand, and in hygrophilous species, the leaves are as a rule flat, with thin epidermal cell-walls, which have plane sides, free stomata, and no wax &c. Water-storing tissue (apart from tropical species) is sparse or absent, and the chlorophyll-tissues have well aerated lacunar spaces. Bast-sclerenchyma is in these cases feebly developed. In the following chapter I have brought together some of the principal anatomical features, in such form that the characters can be employed in checking other determinations of grass leaves. The results, which are based on the elaborate investigations of Duval Jouve, Schroeter, Pée-Laby and Grob, as well as on my own observations, are not complete in all respects, and much more should be done to extend the theme, but the account given will serve to show the student how such results may be employed. It is as yet impossible to decide how far these characters are constant--they are known to be fairly so in many cases--but several grasses cannot yet be distinguished by them alone. [Illustration: Fig. 28. Transverse section of subulate leaf of _Aira flexuosa_ (× about 50), the upper surface represented by a mere ridge with two flanking grooves each with but traces of motor-cells below. One large vascular bundle and four much smaller ones are seen. There are no girders, but slender bands of sclerenchyma at the lower surface nearly join into a continuous sub-epidermal sheath. This type is the extreme form of that in Fig. 26.] It should also be added that some grasses develope two types of leaves (heterophylly), solid or subulate below, flat or slightly inrolled above--e.g. _Festuca heterophylla_--and the following arrangement is intended to apply to the vegetative lower leaves and not to those on the upper parts of the flowering specimen. Moreover the sections should be cut from the basal third of the lamina, and not from the tip of the leaf. CHAPTER V. GRASSES CLASSIFIED ACCORDING TO THE ANATOMICAL CHARACTERS OF THE LEAF. I. THE CHLOROPHYLL-TISSUE, ON TRANSVERSE SECTIONS, IS ARRANGED IN RINGS ROUND THE VASCULAR BUNDLES. THERE ARE MOTOR-CELLS BETWEEN THE RIBS, AND THE STOMATA ARE SUNK AND OCCUR ON BOTH FACES. _Cynodon Dactylon._ The larger lateral nerves have as a rule three smaller ones between each pair, hardly projecting as ribs. Chlorophyll chiefly in a ring round the vascular bundle. Long hairs on lower surface, a few papillæ above. Motor-cells in each shallow furrow. Short cells occur between the long epidermal cells over the bast-region. The Panicums also come here, and differ according to the disposition of the sclerenchyma sheaths around the bundles. II. THE CHLOROPHYLL-TISSUE IS BETWEEN THE VASCULAR BUNDLES, AND NOT CONFINED TO RINGS SURROUNDING THEM. +A. Conspicuous lacunæ between the vascular bundles. Stomata on both faces. Motor-cells occur.+ Lacunæ large and rectangular. Motor-cells confined to a flanking line on each side of the mid-rib. _Glyceria aquatica._ Leaves folded and in section +V+-shaped, hardly keeled, with sclerenchyma at apex. Motor-cells each side of the mid-rib only. The large square or rectangular lacunæ bounded by stellate cells. Papillæ on epidermal cells. Vascular bundles midway between upper and lower surfaces. _Glyceria fluitans._ Section +V+-shaped and keeled, the roof of each polygonal lacuna arched, hence the “ribs” on the upper surface are between the vascular bundles. The latter lie nearer the lower epidermis. The epidermis has papillæ. _Catabrosa aquatica_ and _Hierochloe_ also come here, the former with small lacunæ, the latter with larger ones chiefly towards the upper surface of the leaf. _Digraphis_ is also apt to have a few air cavities near the mid-rib. +B. Lacunæ none, or inconspicuous, the chlorophyll-tissue filling up between the ribs.+ (_a_) Upper and lower leaf-surfaces parallel, or nearly so, and much alike, the ridges being very low or obsolete. Stomata equal or nearly so on both surfaces. (1) Motor-cells absent; vascular bundles feeble and very few. _Mibora verna._ The small leaves are flat, or nearly so, and have three isolated and very feebly developed bundles, devoid of girders or sclerenchyma bands. (2) Motor-cells present, vascular bundles of various orders, with sclerenchyma bands or girders. * _Leaf keeled, and folded--not inrolled. Motor-cells confined to the neighbourhood of the mid-rib. No hairs._ † _Motor-cells conspicuous and conjoined into a band above the mid-rib._ _Dactylis glomerata._ Keel pronounced, with one large vascular bundle and a sclerenchyma band occupying its crest. Motor-cells forming one conjoint band along the upper course of the mid-rib only. Stomata on both faces, but no hairs or thick cuticle. Ribs low, and all bundles have feeble girders. A little sclerenchyma at the margins. A few pale cells in the chlorophyll-tissue. †† _Motor-cells inconspicuous and in two flanking lines, one on each side of the mid-rib._ _Poa trivialis._ Keel with sclerenchyma at its apex, and a small band of the same at the margins. Vascular bundles of three orders, isolated, without girders, but with a small band of sclerenchyma above and below. Ridges obsolete. Short hook-asperities above. No thickened cuticle. Other species of Poa also come here: I cannot distinguish them by the leaf anatomy; but _P. annua_, _P. compressa_, _P. nemoralis_ and _P. pratensis_ are devoid of the hooked asperities; _P. nemoralis_ has a thicker lamina than the rest, and girders to the secondary bundles. _P. annua_ agrees in the latter point. ** _Leaf not keeled: rolling up. Motor-cells distributed between the ridges._ † _Hairs none or rare, or at most a few asperities._ ≡ _Veins numerous, 30-40 on each half lamina. Motor-cells very large._ ⊙ _All vascular bundles with girders above and below._ _Digraphis arundinacea._ No keel. Marginal sclerenchyma conspicuous. A few asperities below. Leaf thin, and all the bundles joined to the epidermis above and below by girders (Fig. 14). Stomata on both surfaces, fairly large: epidermal cells with plane walls. There may be a few irregular air cavities, especially near the mid-rib. ⊙⊙ _Only the principal bundles girdered._ _Arundo Phragmites._ Ridges very numerous and low. No keel. Marginal sclerenchyma strong. Vascular bundles with sheaths of large colourless cells, a few of the strongest girdered below, but most have only sclerenchyma bands above and below. Motor-cells particularly large, between all the bundles. There are no conspicuous lacunæ. Hairs very rare. Epidermal cells small, with sinuous walls: all the cell-walls contain silica. Stomata on both faces, sunk, small and more difficult to see than in _Digraphis_, where the epidermal cells are plane walled, or nearly so. _Arundo Donax_ is very like _A. Phragmites_, but has larger bundles each with a horse-shoe shaped sclerenchymatous mass below, and larger lacunæ. ≡≡ _Veins not more than 10-20 in each half lamina._ ⊙ _More or less conspicuously hairy. The smaller bundles isolated and devoid of girders._ _Bromus sterilis._ Girders to the stronger bundles only. Stiff hairs above and below. Motor-cells poorly developed between each pair of low ridges. No pronounced cuticle. A faint sclerenchyma-band at margin, and at apex of low rounded keel. Stomata on both faces. _Bromus arvensis._ Similar to _B. sterilis_, with stiff hairs commoner below. Harsh in cutting. _B. giganteus_ shows no hairs, but I cannot distinguish the Bromes generally by the leaf anatomy. _Anthoxanthum odoratum._ No keel, ridges obsolete, the stronger bundles only with girders. Motor-cells conspicuous between all the ribs. Marginal sclerenchyma, and that above and below the bundles, poorly developed. A few coarse hairs both above and below, and stomata on both faces. Leaf thin and narrow. _Hordeum murinum._ Few girdered bundles, and sclerenchyma at margins poor. Hairs sparse and coarse. _Bromus asper_, _Brachypodium sylvaticum_ and _Lagurus_ also come here. In all these grasses the epidermal cells are chiefly long, rectangular or slightly hexagonal, with thin and plane walls. ⊙⊙ _Hairs none or very rare on the sections._ _Phleum pratense._ Low rounded ribs with motor-cells between. The larger vascular bundles girdered. Stomata about equal on both faces. No hairs. No keel. Marginal sclerenchyma scanty. _Arrhenatherum avenaceum._ Very rare hairs above: a few blunt asperities here and there. No keel. Ridges low. Girders to the primary bundles, but not very strong: marginal and other sclerenchyma faint, as is also the cuticle. Stomata on both faces. Motor-cells fairly developed between the ridges. _Briza media._ No keel, and mere traces of marginal sclerenchyma. Ribs practically obsolete, but well developed motor-cells in furrows. Principal bundles girdered. Stomata on both sides. No hairs or thickened cuticle. _Avena fatua_, _Molinia_ and _Leersia_ also come here. (_b_) Upper and lower leaf-surfaces dissimilar, or at least not parallel, owing to the conspicuous ridges and grooves above. (1) No stomata below. * _Leaves flat or nearly so, or at least exhibit a conspicuous concave upper surface._ ⊙ _Motor-cells between each pair of ribs: sclerenchyma not forming a continuous layer below._ ≡ _Ridges at least 5-6 times as high as the leaf-thickness between._ _Aira cæspitosa._ Ridges high, 7-10 times as high as the breadth of leaf between, triangular, each with 1-3 vascular bundles devoid of girders, with an upper isolated band of sclerenchyma at the acute tip, and another below the principal bundle. Also small bands below each group of motor-cells. Small conical asperities on the ridges and below. No mid-rib. Stomata on flanks of ridges only, and few motor-cells between (Fig. 23). Each vascular bundle has a sheath, but is isolated. Sclerenchyma at tips of the ridges dense: smaller bands below: strong at margins. Lower cuticle strong. Leaf rolls up. The flat upper leaves of _Festuca rubra_ (Fig. 20) and _F. heterophylla_ are somewhat similar in type. They have stiff hairs on the ridges. ≡≡ _Ridges not more than 2-3 times as high as the tissue between; each furrow with motor-cells, and each vascular bundle joined to epidermis above and below by a sclerenchyma girder._ _Brachypodium pinnatum._ Smooth. Ridges rounded. Hairs rare. The strong sclerenchyma girders below almost continuous laterally. Epidermal cells with sinuous thick walls, and a few tooth-hairs. Note the differences from _B. sylvaticum_, p. 76. _Melica nutans_, _M. uniflora_, and _Calamagrostis Epigeios_ also come here. ⊙⊙ _Motor-cells confined to the innermost 2-4 furrows. Sclerenchyma in a continuous band just inside the thick cuticle below._ _Festuca duriuscula._ The ridges are only about half to one-third as high again as the thickness between, and the motor-cells in four series at the base of the three innermost ridges. Each ridge has only one isolated sheathed bundle, without girders. Stomata on the flanks of the ridges, and few in number. The sclerenchyma forms a thick band just inside the strong cuticle below. The leaf is conduplicate, not convolute. This applies particularly to the more open leaves: the subulate leaves belong to the next type (see Fig. 27). _Aira canescens_ and _Spartina stricta_ also come here. _Psamma arenaria._ Inrolled. Smooth below and devoid of keel, with sub-epidermal band of sclerenchyma, and similar tissue at the margin. Ridges of three sizes, the largest twice or three times as high as the leaf-tissue between is thick, all rounded above, and very hairy. Stomata above only. Motor-cells in each sinus not large. Vascular bundles isolated, without girders or bands of sclerenchyma. _Elymus_ is very like _Psamma_, but has a few stomata below and the sub-epidermal sclerenchyma is not continuous (see Fig. 25). ** _Leaves (subulate) not opening out, the upper surface represented by a groove or a few ridges above the angular or ovate solid section._ ⊙ _Section pentagonal or angular-ovate: sclerenchyma below in a continuous band._ _Aira flexuosa._ Upper surface a depression, with one ridge flanked by two grooves at its base, the depression extending about one-fifth through the whole thickness of the nearly solid leaf. Vascular bundles about 3-5, isolated, sheathed. Sclerenchyma band extending all round the lower surface just inside the thick cuticle. Stomata very few, flanking the ridge; motor-cells in the furrows, poorly developed (Fig. 28). ⊙⊙ _Section elliptical or angular-ovate; sclerenchyma not always in a continuous band below._ _Festuca ovina._ Upper surface a deep fold, with three ridges and 2-4 grooves at its base. Vascular bundles several, with girders. Motor-cells in four series, in the grooves. The lower girders may not fuse laterally into a continuous band of sclerenchyma below (Fig. 18). The folded lower leaves of _F. rubra_ and _F. heterophylla_ come here also. For the flatter leaves of _F. duriuscula_ see p. 78 and compare Fig. 27. The epidermal cells in this series have sinuous thickened walls, and here and there small tooth-like hairs. _Nardus_ also comes here (see Fig. 26). (2) There are stomata below, but fewer than on the upper surface. Motor-cells usually conspicuous between the ridges. * _Stronger bundles with girders of sclerenchyma joining them to the epidermis, at least below._ ⊙ _Hairs sparse or none._ _Cynosurus cristatus._ Mid-rib obsolete, except the strong vascular bundle. Ridges low and rounded, with 2-4 flanking stomata, and well developed motor-cells in furrows. Secondary vascular bundles with strong girders below, the smaller bundles sheathed only and isolated. Each ridge with slight sclerenchyma above. A few stiff short hairs above, and the leaves are convolute. Ridges about twice the height of the leaf-thickness between (Fig. 16). _Agropyrum repens._ Mid-rib and margin with strong sclerenchyma-groups: ridges unequal, low and rounded and each vascular bundle girdered. A few pointed hairs above, and motor-cells in all the grooves. A slight keel, stomata on both surfaces. _Agropyrum caninum._ All the bundles have girders. Slight keel. Marginal sclerenchyma. Few, very short, hard, hooked asperities above and below. Ridges low, and motor-cells poorly developed between. Few stomata on lower surface. Very like _A. repens_, but the principal ridges are more prominent below and those nearer the mid-rib have asperities. _A. junceum_ resembles _Psamma_, but the ridges are much lower, and there are a few stomata on the under surface (Fig. 24). ⊙⊙ _Leaf obviously hairy._ † _Hairs more especially above._ _Avena flavescens_ is very similar to _Cynosurus_, but is evidently hairy, and _A. pratensis_ also comes here. †† _Hairs abundant on both surfaces._ _Holcus lanatus._ Very hairy above and below, and at the margins. Slight keel with sclerenchyma band: sclerenchyma at margin slight. Ridges rounded, about twice as high as thickness between. Stomata more abundant above. Cuticle very thin and leaf soft. All bundles except the mid-rib with girders. Motor-cells fairly well developed between the ridges (Fig. 15). _Kœleria cristata._ Very hairy on both surfaces. Ridges irregular, the largest flat and high, the others rounded or triangular. Vascular bundles isolated, and the sclerenchyma reduced to a few cells in a single layer beneath the epidermis at the apex of each ridge and below the bundle. Motor-cells well developed in each furrow. Stomata more numerous above. ** _No girders to the vascular bundles._ _Lolium perenne._ Ridges numerous and unequal. Vascular bundles sheathed and isolated--i.e. devoid of girders: small patches of sclerenchyma at the apex of each stronger ridge, and on the opposite side below only. No hairs. _Lolium temulentum_ is similar but is more apt to be convolute, whereas _L. perenne_ is more folded. _Alopecurus pratensis._ Leaf thin and somewhat like _Phleum_, but the ridges somewhat higher and more rounded, and only the principal bundles girdered below. Stomata on both faces. _Festuca elatior_, _Bromus giganteus_ and most species of _Agrostis_ come near _Lolium_. See Figs. 17, 22. CHAPTER VI. GRASSES IN FLOWER. When the flowering shoot of a grass pushes up into the light and air from the enveloping leaves, it forms a more or less branched collection of flowers known as the _Inflorescence_, and in all our grasses this inflorescence consists of a principal stalk, _haulm_ or _culm_, on which shorter stalks--branched or not--are arranged. The mode of branching is usually such that the youngest branches are nearest the top, and the oldest nearest the bottom. It is evident at once, on comparing the Moor Mat-grass (_Nardus_), Vernal-grass (_Anthoxanthum_), Cock’s-foot (_Dactylis_), Meadow-grass (_Poa_) that considerable differences exist as to the extent of this primary branching of the inflorescence. In _Nardus_ (Fig. 2) we find a number of long cylindrical-tapering bud-like structures each seated on one side of the principal stem, and one over the other: in the Vernal-grass and Cock’s-foot we find tufts of such bud-like structures closely crowded round the upper end of the principal stalk, the whole forming an elongated tuft of tufts: in the _Poa_ we find a number of radiating, slender, long branches springing from the principal stalk, and each of these ramifies again, and yet again, until each of the ultimate hair-like branches bears one of the bud-like structures. See also _Catabrosa_ (Fig. 4). [Illustration: Fig. 29. A spikelet of _Festuca elatior_, var. _pratensis_, from which the glumes and one palea (the outer) have been removed to show the flower in situ (× 12). The two lodicules are in front: the inner palea behind. Strasburger.] The first thing for the student to apprehend is the nature of the bud-like structures referred to. Each of these is in itself a small tuft or bud of leaflike organs or scales arranged on a short twig (_Rachis_, _Rachilla_), as it were, and is called a _Spikelet_, and the true flowers of the grass are contained in the angles between the scales--the scales being popularly known as “_chaff_”: technically as _Glumes_ and _Paleæ_. In order to understand the structure of a spikelet the student should carefully dissect a large one, such as that of an Oat (Fig. 1). Proceeding from outside, he will find two large scales, like two boats, fixed below to the stalk (_rachis_) one just below the other, and shutting together as if hinged. These are called the _glumes_--the inner and outer glume respectively--and they enclose the rest of the spikelet. [Illustration: Fig. 30. Diagram of a spikelet of a grass as it would appear if the internodes between each set of organs were elongated. _g^1_ lower and _g^2_ upper glume. _P_ lower and _p_ upper palea of the second oldest flower _F^2_. _f_ a barren flower represented only by the axis and paleæ. Above it a single palea and the termination of the axis (_a_) of the spikelet.] Inside them the axis or stalk (_rachis_) is continued for a short distance only and on its sides are hinged two other pairs of more or less boat-shaped scales, smaller and more delicate than the glumes, and known as the _pales_ (_paleæ_), while a third pair of still smaller pales is fixed to the end of the axis. In each case one smaller and more delicate _inner_ palea is hinged just inside its more obvious _outer_ palea. In the closed condition of the spikelet each of the three pairs of pales is shut together, and pressed close to the axis, and the pair of glumes shut in the whole. On opening each of the lower pairs of pales we find a _flower_ inside; but the terminal pair usually contain only the barren end of the axis. Hence the latter is barren and the former are fertile. Each fertile flower is found on careful dissection to consist of a small swollen _Ovary_, or young grain, covered with silky hairs and with a couple of delicate plumes (the _Stigma_) at its apex, and three long and slender _Stamens_; while the magnifying glass will show two tiny scales at the base--the _Lodicules_. All our ordinary grasses have their flowers thus constructed--a pair of _lodicules_, three dangling _stamens_ and an _ovary_ with a feathery two-plumed _stigma_: each such flower is also enclosed in its pair of _pales_, and the several pairs of pales of each spikelet, with their contents, are enclosed in the pair of _glumes_ (Figs. 29-32). Returning now to the inflorescence. It is clear that we have to distinguish between the entire branched total Inflorescence, and the Spikelets or partial inflorescences of which it is composed. In Botany it is agreed to call any inflorescence consisting of a stalk or axis on which the flowers are arranged without stalks--i.e. sitting directly on it--and so that the youngest are above and the older below, a _Spike_, and each spikelet is _a little spike_. [Illustration: Fig. 31. Diagram of a spikelet of Wheat dissected (× about 5) showing--from below upwards--the two glumes, two paleæ, two lodicules, three stamens, and the ovary of the typical grass. Oliver.] [Illustration: Fig. 32. Diagram of a spikelet of _Anthoxanthum_ dissected (× about 8), and showing--from below upwards--two outer and two (awned) inner glumes, two paleæ, two stamens, and the ovary. There are no lodicules. Oliver.] On looking at the total inflorescence of the _Nardus_ we see that we have a number of spikelets seated on the sides of an axis: this is then a spike of spikelets, or, shortly, a _Spike_[9] (Fig. 5). _Mibora_ and _Lepturus_ afford other examples. In _Panicum_, _Cynodon_ (Fig. 2) and _Spartina_ we have groups of such spikes. The _Poa_ inflorescence is, however, different. It consists of a loose branched system of spikelets. Botanists term such a loosely branching system, where each branch ends in a flower, a _panicle_: here then we have a panicle of spikelets, or, shortly, a _Panicle_. _Aira_, _Agrostis_, _Calamagrostis_, _Avena_, _Catabrosa_ (Fig. 4) and many others afford further examples. In _Dactylis_ we have a condition of affairs between the two extremes given: the inflorescence is not so close a spike as _Nardus_, and not so open a panicle as _Poa_--it is rather a spike-like panicle, partaking of the nature of both. A special type of this (Foxtail) occurring in certain grasses--e.g. _Phleum_, _Alopecurus_, _Phalaris_ and _Lagurus_,--is so characteristic as to be worth noting (Fig. 3). There is also another aspect of these inflorescences which is not without interest as showing how diagnostic characters may be obtained from purely external features, easily observed in the field. We have seen that in _Nardus_ the spikelets are arranged on one side only of the rachis, or main axis, so that about three quarters of the circumference of the latter is bare; whereas in _Lolium_--with which _Agropyrum_ and _Brachypodium_ agree in this respect--the spikelets are on opposite sides, leaving the intervening two quarters, i.e. half its surface, of the circumference of the axis naked. In _Cynosurus_ and the simpler forms of _Dactylis_, we find the spikelets crowded round about three quarters of the surface of the rachis, leaving the fourth quarter naked; and, finally, in _Phleum_, _Alopecurus_, _Hordeum_, and _Anthoxanthum_ the spikelets cover the entire surface. In the first (_Nardus_) and third examples (_Cynosurus_, _Dactylis_) where the spikelets are turned to one side, the inflorescence is said to be _secund_. The next point to notice is that not every grass has so many as two fertile flowers and one barren one in its spikelet, as the Oat has. A spikelet may have one (_Phleum_), two (_Aira_) or three (_Avena_) or more (_Poa_) fertile flowers, and no barren ones or several, the number of flowers being counted by the number of pairs of pales found inside the pair of glumes. Moreover every flower is not necessarily fertile (e.g. _Arrhenatherum_, _Holcus_) and several grasses have one or more flowers in each spikelet containing _stamens_ only--male flowers--while others may have _ovaries_ only--female flowers. In some exotics the male and female flowers are on different parts of the same plant (Maize) or even on different plants (_Gynerium_), an arrangement not met with in our grasses. Accordingly, it is of importance in determining a grass to discover how many flowers the spikelet contains, and whether any are male only, or barren, &c., as well as to make out the character of its inflorescence. In the following lists I have brought together some of the chief points with illustrative examples. SPIKELETS with only one perfect flower (without rudimentary ones). _Psamma._ _Milium._ _Nardus._ _Alopecurus._ _Phleum._ _Hordeum._ _Agrostis._ And species of the rare grasses _Calamagrostis_, _Mibora_, _Lepturus_, _Spartina_, _Cynodon_, _Gastridium_, _Lagurus_, _Polypogon_, _Leersia_. SPIKELETS with one perfect flower and one or more male or rudimentary ones. _Digraphis._ _Anthoxanthum._ _Holcus._ _Arrhenatherum._ And the rare genera _Hierochloe_ and _Panicum_. SPIKELETS with at least two perfect flowers. _Molinia._ _Arundo._ _Avena._ _Aira_ (some species). _Bromus._ _Cynosurus._ _Dactylis._ _Triodia._ _Sesleria._ _Kœleria._ _Melica_ (one species). _Briza._ _Poa trivialis._ _Catabrosa._ SPIKELETS with at least three perfect flowers and usually more. _Elymus._ _Agropyrum._ _Brachypodium._ _Lolium._ _Festuca._ _Poa._ _Glyceria._ INFLORESCENCE, a spike of single spikelets. _Agropyrum._ _Brachypodium._ _Lolium._ _Nardus._ And varieties of _Festuca Myurus_ and _F. loliacea_, &c. INFLORESCENCE, a spike of pairs or tufts of three or more spikelets. _Elymus_ (pairs). _Hordeum_ (threes). _Cynosurus_ (clusters). INFLORESCENCE, a cylindrical closely tufted spike-like panicle. _Phleum._ _Alopecurus._ _Psamma._ _Anthoxanthum._ INFLORESCENCE, a compact more or less tufted panicle. _Molinia._ _Kœleria._ _Triodia._ _Dactylis._ _Aira præcox._ _A. canescens._ _Sesleria._ And rare grasses like _Polypogon_, _Gastridium_, &c. INFLORESCENCE, a loose plume-like or branched panicle. _Avena._ _Bromus._ _Arrhenatherum._ _Catabrosa._ _Aira_ (except _A. præcox_ and _A. canescens_). _Arundo._ _Digraphis._ _Milium._ _Agrostis._ _Melica._ _Holcus._ _Poa_ (most of the species). _Glyceria._ _Briza._ _Festuca_ (except _F. Myurus_). And the rare _Hierochloe_. The _Glumes_ are always present in our grasses, and rudimentary only in the rare grass _Leersia_; but _Lolium_ and _Nardus_ have only _one_ glume to the spikelet, and _Hierochloe_, _Digraphis_ and _Anthoxanthum_ (Fig. 32) have four or six. Our other grasses have _two_, but often unequal in size. In shape they are usually boat-like, pointed or obtuse (_Briza_) and frequently with a distinct keel (_Anthoxanthum_, _Digraphis_, _Phleum_, &c.) or with ridges, green lines (veins) and other characteristic markings (e.g. _Digraphis_). The tip may be extended into a stiff long point or awn (_Agropyrum_, _Phleum_, _Nardus_) and the keel, ribs, and awn may have hairs or serrulæ on them. The rule is, however, that the glumes are not awned. In texture the glumes may be herbaceous and green-brown or purple (e.g. _Melica_) or membranous or stiff, or scarious (i.e. browned, as if scorched) at the edges. In _Hordeum_ some of the glumes are so narrow and pointed as to resemble stiff awns. In _Catabrosa_ the glumes are truncate, as if bitten off at the top. The _Paleæ_ are also often more or less boat-shaped, or flat ovate or oblong scales, usually more delicate than the glumes and frequently pointed, or (especially the outer pale) awned at the tip: in some cases, however, the awn springs from the middle or base of the back of the pale, and the latter may be bifid at its apex. The pale has usually a distinct middle nerve. The inner pale is commonly the smaller and more delicate of the two, and is sometimes difficult to see. CONSPICUOUSLY AWNED GRASSES. _Avena._ _Arrhenatherum_ (Fig. 33). _Hordeum._ _Bromus._ _Agropyrum caninum._ _Lolium temulentum._ _Brachypodium sylvaticum._ _Festuca Myurus._ And a few rare grasses like _Panicum_, _Polypogon_, _Lagurus_. GRASSES WITH NO TRUE AWNS. _Kœleria. Milium. Digraphis. Elymus. Festuca_ (except _F. Myurus_ and _F. uniglumis_). _Briza. Poa. Glyceria. Catabrosa._ _Molinia. Melica. Psamma. Agrostis alba._ And a few rare forms like _Leersia_, _Hierochloe_, &c. GRASSES WITH INCONSPICUOUS AWNS, OR MERE POINTS, TO SOME OF THE GLUMES OR PALES. _Arundo._ _Phleum._ _Alopecurus._ _Holcus._ _Nardus._ _Agropyrum repens._ _Lolium perenne._ _Brachypodium pinnatum._ _Dactylis._ _Cynosurus._ _Sesleria._ [Illustration: Fig. 33. _Arrhenatherum._ 1 unopened and 2 open anther (× 12). 3, spikelets open and exposing the stamens and stigmas; 4, the pollen escaping and being dusted on to the stigmas (× about 5). Kerner.] As regards the flower proper, all our British grasses except _Anthoxanthum_ (which has two only) have three stamens; but many exotic grasses have six stamens, and a few have a large number--even 40. The stamens have slender filaments and large versatile anthers, which dangle from between the paleæ when the flowers are mature, scattering their clouds of fine pollen in the wind (Fig. 33). All our ordinary grasses except _Nardus_--where there is a simple straight hairy style--have two spreading feathery stigmatic plumes, which stand out right and left from between the paleæ when the pollen is flying about on the wind. (Fig. 33.) Much interesting speculation has been expended in attempting to explain the morphological or theoretical significance of the parts of the spikelet of a grass. If we project the various organs on a flat surface in the form of a plan, keeping their relative positions intact, we obtain a diagram such as that shown in Fig. 34. [Illustration: Fig. 34. Diagram of a spikelet of a grass. The two glumes--_g^1_ outer, _g^2_ inner--embrace four flowers, of which 1 is the lowermost and 4 the uppermost.] The comparison of numerous cases, and the study of the development of the parts on the microscopic growing point dissected out from young buds, have suggested that the inner and outer glumes are bracts, or covering leaves, at the base of the true spikelet. In like manner the two paleæ are bracteoles which subtend the flower proper. On this assumption they can be compared with the corresponding structures in other plants; whereas any attempt to compare the paleæ or glumes with the sepals and petals of ordinary flowers breaks down. A curious interest attaches to the awns so often found on the backs of paleæ, and especially to those where the (sub-terminal) awn springs from just below the bifid apex (e.g. _Avena_, &c.). Hackel showed by comparison with a rolled leaf attached to its sheath and ligule (e.g. _Psamma_) that such an awn as that of _Bromus Alopecurus_ attached to its palea stands in the relation of a leaf to its sheath, the part of the palea above the insertion corresponding to the ligule, the awn itself to the lamina, and the palea below its insertion to the sheath. This view is rendered the more probable by the anatomy of the awn and by the observations of Schmid, who has shown that the awns of cereals contain chlorophyll-tissue and a vascular bundle, and have stomata, and his experiments led him to conclude that in the young condition they transpire and assimilate, and probably even contribute to the nutrition of the ripening grain. When dry and mature the awns subserve biological functions of quite another kind, and as we shall see are of importance in the distribution and sowing of the grains. (Fig. 42.) Returning to the floral diagram, we see that the two lodicules, the three stamens and the ovary still remain to be explained. Much discussion has been held regarding the lodicules. Functionally they are said to aid in the divarication of the paleæ when the period of anthesis arrives, and the stamens and stigmatic lobes are to be exposed, by swelling and driving the valve-like paleæ apart. Morphologically they have been explained as representing the rudimentary perianth, here reduced to two minute scales, but in some exotic grasses (_Bambusa_, _Stipa_, &c.) three lodicules, or even more, are present. (Figs. 35, 36.) On the other hand they may be, and probably are, scales of the nature of minute bracteoles and of no significance to the flower itself. [Illustration: Fig. 35. Floral diagram of ordinary grass. Each pair of paleæ--_i.p._ inner and _o.p._ outer palea--encloses three stamens (_s_), two lodicules (_l_) and the ovary. _st_, stigmatic plumes. _a_, axis.] [Illustration: Fig. 36. Floral diagram of a Bamboo, showing six stamens, three inner (_i.s._) and three outer (_a.s._), and three lodicules (_l_) in addition to the ovary. _i.p._ inner and _o.p._ outer palea. _a_, axis.] If this is so the flower of the grass is perfectly naked, and consists in the typical case of three stamens and one carpel. The development of the ovary lends no support to the view that there are two carpels: the stigmatic plumes are not separate styles. Nor does the fact that some grasses have six stamens lend support to the idea that the flower is derived from the trimerous type so common in Monocotyledons: other numbers may occur--e.g. as few as two (_Anthoxanthum_, Fig. 32) or even one only (_Uniola_, _Cinna_, &c.) or as many as 20 or 40 in certain other exotic grasses. Even when three stigmatic plumes are developed, as in some Bamboos, close investigation does not confirm the view that the ovary consists of more than one carpel. We must therefore regard the flower of the grass as typically composed of one carpel and three stamens, with no perianth whatever. It is subtended by one or more bracteoles (the lodicules), and enclosed in a pair of bracteoles one higher than the other (the paleæ). The glumes are bracts of the partial inflorescence--the spikelet. That there are some departures from this type in detail does not invalidate the importance of the fact that most grasses conform to it. I now pass to the consideration of a grouping of our ordinary grasses according to their floral arrangements. The student should distinctly understand that the following notes are intended to serve as an introduction to the floral characters of our grasses, and not to replace the study of the Flora. I have dealt with this section of the subject less in detail, because our best Floras give so much information that it seemed undesirable to do more than attempt to guide the reader in the recognition of the genera and principal species by means of external features easily observed by anyone with a little care. The detailed and critical examination of species, varieties and rare forms should always be done with reference to a complete Flora. CHAPTER VII. GRASSES GROUPED ACCORDING TO THEIR FLOWERS AND INFLORESCENCES. I. GRASSES WITH ONLY ONE PERFECT FLOWER IN THE SPIKELET. +(1) Inflorescence spikate[10].+ +A. Inflorescence a spike of simple spikelets.+ _Nardus stricta_, L. A tough wiry tufted moor-grass, with setaceous leaves, secund spikelets with a single rudimentary glume, and a stiff simple hairy style. (Fig. 2.) The much rarer _Mibora verna_ about three inches or so high, and _Lepturus_, both with flat leaves, also come here. Certain superficial resemblances in the habit or inflorescence in _Festuca Myurus_ and rare forms like _Spartina_, may occasionally cause hesitation until the spikelets are examined. +B. Spike with sessile or sub-sessile tufts of three or more spikelets.+ (_a_) A spike of tufted awned spikelets, in triplets at each notch of the rachis, and one or two of each triplet barren. +Hordeum.+ No other genus of our grasses is like _Hordeum_. The purely superficial resemblances in the inflorescences of _Polypogon_, _Lagurus_, and _Cynosurus echinatus_--all extremely rare species--disappear at once on examination. In _Bromus erectus_ the equally superficial resemblance is due to the stiff awns: the spikelet has six to twelve flowers and is stalked. It should also be noted that _Hordeum sylvaticum_ occasionally has a rudimentary second flower in the lateral spikelets (see note p. 105). (α) A shade-grass with the central spikelet only imperfect; staminate, or rudimentary, or entirely wanting. _H. sylvaticum_, Huds. (β) The central spikelet is the perfect one, the two lateral barren. Growing in open land. (i) _A perennial meadow-grass. All the glumes scabrid and bristle-like._ _H. pratense_, Huds. (ii) _Annuals with some of the glumes at least, lanceolate or broad below._ * _Ruderal plant, with cylindrical spikes, long awns; glumes of the central flower dilated below._ _H. murinum_, With. ** _Maritime plant, more or less glaucous, with short ovoid spikes: glumes of the central flower bristle-like._ _H. maritimum_, With. (_b_) Spike cylindrical, of sessile or nearly sessile awned spikelets, densely crowded round the axis, the whole resembling a fox’s brush or cat’s tail. Species of _Lagurus_, _Polypogon_, _Phalaris_ (not truly awned), _Panicum_ (with bristles between the spikelets), and _Gastridium_ are other British grasses approaching this type of inflorescence: they are all rare or very local. _Sesleria_ has an ovoid spike, but the spikelets are two-flowered and not truly awned. _Kœleria_ may present resemblances, but the spikelets are very different in detail (see p. 109). (i) _Awns inserted into the back of the single palea, and hair-like. Glumes connate below, keeled. Only one palea._ +Alopecurus.+ * _Annual corn-weed, with a long and slender spike, pointed above. Glumes almost glabrous, and connate to the middle._ _A. agrestis_, L. ** _Perennials, with shorter and stouter spikes, rounded above. Glumes connate at the base only, and obviously hairy on the keel._ † _Procumbent and kneed at the nodes below. Spike 1-2 inches long. In marshy places._ _A. geniculatus_, L. †† _A meadow-grass, with erect stems, and spikes 2-3 inches or more and stouter._ _A. pratensis_, L. The rare _A. alpinus_, Sm. with short ovoid spikes, about one inch long, only occurs in the Highlands. (ii) _Awns, when present, merely the stiff, pointed termination of the keel. Glumes free below. Paleæ two._ * _A glaucous shore plant with long creeping stolons (sand-binder). Inflorescence harsh, 5--6 inches long. Glumes tapering, simply acute._ _Psamma arenaria_, Beauv. _Elymus_, a much rarer sand-binder of similar habit, may lead to confusion until the 3--4 flowered spikelets and different arrangement are observed. (See p. 108.) _Agropyrum repens_ (var. _junceum_) is similar in habit and station, but its spikes and spikelets are very different (see p. 107). _Phleum arenarium_ is much smaller (see below). ** _Erect. Inflorescence rarely longer than three inches. Spikelets flat: glumes keeled, the keel suddenly produced into a sharp stiff awn or mucronate point. Paleæ two._ +Phleum.+ † _Tall perennial meadow-grass. Awn bristle-like, almost as long as the nearly glabrous glume: spike long, cylindrical._ _P. pratense_, L. †† _Small, compact annual shore plant, with the glumes acute only and the keel ciliate above. Inflorescence not more than 1--1-1/4 inch long._ _P. arenarium_, L. The rare _P. Bœhmeri_, Schrad. has the glumes merely tapering to a sharp point; and the rare _P. alpinum_, L. has a much shorter spike and glumes ciliate on the keels. The rare _P. asperum_, Jacq. has broad, shortly mucronate glumes and a longer and more slender spike. +(2) Inflorescence a panicle--i.e. tufts or spreading stalked groups of spikelets are arranged on the main axis.+ +A. Inflorescence compact and irregular; a spike of tufts (spike-like panicle). Glumes four, the inner pair awned: paleæ minute. Stamens two only.+ _Anthoxanthum odoratum_, L. The four glumes and two stamens distinguish this grass at once. Other grasses with occasionally tuft-like inflorescences--e.g. species of _Agrostis_, _Gastridium_, _Aira_, _Dactylis_, _Cynosurus_, _Poa_, _Triodia_, _Kœleria_--are distinguished at once by having three stamens (_Bromus_ occasionally has but two), only two glumes, several flowered spikelets, &c. +B. Inflorescence a distinctly branched panicle, more or less loose and spreading.+ (_a_) Tall reed-like perennials, growing in water or in marshes, with plume-like inflorescences, and silky hairs at the base of the paleæ. Glumes with a keel and point, but not awned. (i) Spikelets purplish: outer palea with a slender dorsal awn: basal hairs longer than the paleæ. Leaves narrow. Not common. _Calamagrostis Epigeios_, Roth. (ii) Spikelets greenish. No awns: basal hairs much shorter than the paleæ. Leaves broad. Common. _Digraphis arundinacea_, Trin. A variety of _Digraphis_ with white stripes in the leaves is grown in gardens. Other aquatic reed-like grasses are _Arundo_ and _Glyceria aquatica_: both have several flowers in the spikelet. The rare _Calamagrostis lanceolata_, Roth., _C. stricta_, Nutt. and _C. strigosa_, Hartm. also come here. (_b_) Slender grasses, not reed-like, with delicate loosely spreading panicles of small spikelets. (i) A tall, slender shade-grass, in woods. Paleæ very smooth and glistening. Spikelets few, distant and turgid, awnless. _Milium effusum_, L. _Melica uniflora_, also a wood-grass, has the spikelets two-flowered, though the upper one may be a mere rudiment, and much fewer, on a flexuous nodding axis. The much rarer _M. nutans_ has two perfect flowers in the spikelet (see p. 105). (ii) Grasses of open situations, with numerous small pointed spikelets. Inner palea minute or absent. +Agrostis.+ The genus most likely to give trouble here is _Aira_, which though normally with two flowers in the spikelet, occasionally has but one. As regards the common species of similar habit, &c., _Aira_ has bristle-like leaves and _Agrostis_ flat ones. Again, _Agrostis alba_ has no protruding awn, as in the spikelets of _Aira_. For _Aira cæspitosa_ and other details, see p. 117. * _Awnless, or at most a short bristle not equalling the palea. Leaves flat and short._ _A. alba_, L. An exceedingly variable plant. The variety _A. stolonifera_ has a less spreading panicle, and broader leaves with a long serrated and pointed ligule: the variety _A. vulgaris_ has a spreading loose panicle, narrower leaves, and a short truncated ligule. There is, however, much difficulty in distinguishing the intermediate forms on mountain-pastures, &c. ** _Distinctly awned. Leaves narrower, the lower ones inrolled and almost setaceous._ _A. canina_, L. The rarer _A. setacea_, Curt. with subulate leaves and _A. Spicaenti_, L. with long awns also come here. The lax spreading type of panicle characteristic of _Aira_ and _Agrostis_, &c., described above, occurs in species of _Avena_, _Bromus_, _Briza_, _Poa_ and _Catabrosa_, but the basal silky hairs and twisted awns (_Avena_), long sub-terminal bristle-awns (_Bromus_), habit (_Catabrosa_), and the presence of two, three, or more flowers in the considerably larger spikelets of all, easily distinguish them. The rare grasses _Leersia_, with two glumes and no paleæ, and _Gastridium_, with curiously bullate bases to the glumes, also come into this group with one-flowered spikelets, but their characters must be studied with the flora. The same remark applies to species of _Panicum_, _Cynodon_, _Spartina_ and other aliens, occasionally met with. II. GRASSES WITH AT LEAST TWO FLOWERS--OF WHICH ONE MAY BE IMPERFECT--IN THE SPIKELET. +A. Only one perfect flower, the other staminate only or altogether rudimentary. Inflorescence a loose or racemous panicle.+ In _Hordeum sylvaticum_ the two lateral spikelets occasionally conform to this heading (see p. 100), and the same is said to be the case sometimes in _Aira_ (see p. 104). The rudiments are extremely minute, however, and hardly suffice to justify the removal of these grasses to this group. In one or two species of _Aira_ the panicle may be somewhat contracted and tuft-like. The very rare _Hierochloe_ has one perfect flower, and two lower staminate ones in each spikelet. (_a_) A shade-grass found in woods. Awnless. One flower perfect, the other (upper) reduced to a small stalked knob. Inflorescence racemous. _Melica uniflora_, L. The much rarer _M. nutans_ has two perfect flowers and a similar rudiment (see note, p. 104). (_b_) Grasses of open situations, spikelets with awns. The reduced flower staminate. * Upper flower perfect, lower staminate only. Tall oat-like meadow-grass, with a bent and twisted dorsal awn to the outer palea of the lower flower: silky hairs at the base of paleæ. _Arrhenatherum avenaceum_, Beauv. The grasses most like this are species of _Avena_ and _Aira_. The former have two or more perfect flowers, and the only broad-leafed _Aira--A. cæspitosa_, see p. 117--is easily distinguished by its leaves and its very small spikelets and short simple awns. ** Upper flower staminate: lower perfect. Small hairy grasses, with red-veined basal leaf-sheaths and short simple awns. +Holcus.+ † _Erect, evenly hairy, glumes blunt, awn not protruding. Common._ _H. lanatus_, L. ††, _More or less procumbent, hairs chiefly at the nodes. Glumes pointed. Awns simple and exserted. Rarer._ _H. mollis_, L. +B. Each spikelet with at least two perfect flowers, often more.+ (+1+) +Inflorescence spikate, the main axis bearing sessile or sub-sessile spikelets, each containing three or more flowers.+ (_a_) Spike simple[11], axis stout and notched, each notch having one spikelet closely sessile in it. (_i_) Spikelets distichous, the flat side of each--i.e. the edges of the glumes--being next the axis (rachis). +Agropyrum.+ * _A weed with creeping stolons, and no awns or mere points to the glumes._ A. _repens_, Beauv. The variety _A. junceum_ found as a sand-binder on sea-coasts is glaucous, stiffer, with sharply pointed leaves, and blunt glumes. For other sand-binders see note, p. 102. ** _Not creeping. Awns long and prominent._ _A. caninum_, Beauv. (ii) The rounded backs of the glumes are next the rachis. * _Spikelets flat and closely sessile in the notches of the rachis._ +Lolium.+ † _Awnless or nearly so. Perennial._ _L. perenne_, L. †† _With conspicuous awns. Annual, not common._ _L. temulentum_, L. There are several cultivated varieties of _L. perenne_: _L. temulentum_ is notoriously poisonous (see note, p. 168). The lowermost glume of each spikelet is often alone developed or conspicuous, and looks like a bract in the axis of which the spikelet sits. ** _Spikelets elongated and hardly flattened, and not quite sessile, especially the lower: rachis scarcely notched, the spikelets with their sides (edges of glumes) next the axis._ +Brachypodium.+ † _A shade-grass with long, conspicuous awns to the more or less drooping spikelets. Common._ _B. sylvaticum_, Beauv. †† _Growing in the open. Spikelets stouter, stiffer and more erect, with short awns. Not common._ _B. pinnatum_, L. _Brachypodium_ may easily be confounded with _Bromus_, but the spikelets are nearly sessile: their shape and the absence of conspicuous notches distinguish this genus from _Agropyrum_. _Lolium_ has a conspicuously notched rachis and the spikelets arranged in the other plane. _Poa loliacea_, Huds., an uncommon sea-shore weed, may also be placed here; as also _Festuca elatior_, var. _loliacea_, Curt. and some forms of _Bromus arvensis_, var. _mollis_, L. No other British grasses resemble _Brachypodium_: any superficial likeness remarked in species of _Hordeum_, _Festuca_, &c. disappears at once on examination. (_b_) Spike compound--i.e. with clusters of two or more sessile or sub-sessile spikelets arranged along the rachis. (i) Spike elongated, fertile spikelets with 3-5 flowers. * _Pasture-grass with wiry rachis, on which the spikelets are secund and sessile in clusters: in each cluster a comb-like group of barren glumes subtends one of fertile spikelets._ _Cynosurus cristatus_, L. The rare _C. echinatus_ has the pectinate groups of barren glumes even more prominent. ** _Stout glaucous sand-binder with pairs of spikelets sessile in the notches of the rachis, and all fertile. Spike cylindrical. Not common._ _Elymus arenarius_, L. For other sand-binders see p. 102. The only grass likely to be confounded is _Agropyrum_, in which the spikelets are not paired. _Lolium_, _Brachypodium_, &c. are easily distinguished. (ii) Spike short and ovoid: spikelets sub-sessile and imbricate, in clusters. Bluish. _Sesleria cærulea_, Ard. Not easily mistaken for any other grass. As some of the spikelets are shortly stalked, the inflorescence is strictly paniculate, but the fact is not obvious. The glume-like bract at the base of the spike, and the general appearance suggest resemblances to certain moor-sedges at first sight. The only other grasses with similarly shaped spikes are species of _Alopecurus_, _Phleum_, and the rare _Lagurus_, _Polypogon_, _Phalaris_, _Panicum_, all with very different spikelets and easily distinguished. (+2+) +Inflorescence a panicle or raceme--i.e. the spikelets on evident stalks, simple or branched, from the main axis.+ It does not follow that every spikelet is distinctly stalked, and cases occur where the stalks are very short and stiff: when this happens to the stalks arising from the main axis, and the latter is elongated, the type of the spike is closely approached, and the inflorescence resembles that of _Brachypodium_, _Lolium_, &c. In some depauperated varieties of _Poa_, _Festuca_, &c., an actual spike results (see note, p. 111): the number of flowers in the spikelet is important. _a_) Panicle short, contracted and tuft-like, owing to the shortness and stiffness of most of the stalks and their tendency to remain erect, at least until anthesis. Glumes keeled and ending in a point. (i) _Panicle with a few branches, at first erect, ending in tuft-like secund clusters. Spikelets harsh, with 3-5 flowers. Coarse meadow-grass._ _Dactylis glomerata_, L. Not easily confounded with any other grass if attention is paid to the folded coarse leaves, the tufted perennial habit, and the harsh inflorescence, the glumes on the spikelets being stiffly hairy on the keel. (ii) _Panicle contracted, more or less ovoid or cylindroid, but most of the spikelets stalked, and not aggregated into dense clusters, spikelets silvery, containing 2-3 flowers._ _Kœleria cristata_, Pers. Any resemblances to forms of _Aira_ are at once nullified by the absence of true awns in _Kœleria_. _Festuca_ and _Poa_ have more numerous flowers in the spikelet. _Anthoxanthum_ has only one flower, with two stamens, in the spikelets. _Phleum_ and _Alopecurus_ present resemblances, but see pp. 101 and 102. (_b_) Panicle elongated and lax--i.e. all or most of the spikelets on distinct slender stalks, longer than themselves. (i) _Panicle close: the spikelets on distinct and even long stalks, but the latter erect and keeping the spikelets near the main axis._ In some cases the stalks from the main axis bear only one spikelet each and the type of inflorescence is that of a raceme; usually, however, one or more of the lowermost stalks branch and disclose the panicle. * Panicle with few simple branches, racemous, each spikelet large and containing about four flowers, palea three-toothed at the apex. A small heath-grass, with hairs at the ligule. _Triodia decumbens_, Beauv. The inflorescence may have some resemblance to _Melica_ (see p. 105), but the four-flowered spikelet, ligule, habitat and stature distinguish it at once. ** Panicle with divided branches, which are more or less erect. † Spikelets awnless. ⊙ _Spikelets small, purplish, with two or at most three florets; the upper on a stalk. Coarse moor-grass._ _Molinia cærulea_, Mœnch. ⊙⊙ _Spikelets with six or more florets._ ‡ _Tall aquatic grass with long, lax, narrow panicle and spikelets, somewhat nodding, and with 8-20 flowers in each._ _Glyceria fluitans_, Br. The only similar grass is _Glyceria aquatica_, Sm. which differs in its more reed-like habit, open panicle, and fewer flowers. ‡‡ _Small land-plants not more than a foot high, with short, stiff, somewhat crowded panicles, and spikelets containing 6-8 flowers._ ≡ _Maritime perennial with creeping stolons, and about a foot high: panicle somewhat open below._ _Poa maritima_, Huds. ≡≡ _Inland plant with secund panicle, about six inches high._ _P. rigida_, L. The rare _P. procumbens_, Curt. and _P. bulbosa_, L. also come here, as well as starved forms of _P. compressa_, L. Some forms of _Festuca elatior_, var. _pratensis_, Huds. growing in dry situations may give trouble, and will have to be examined with the flora. See also note, p. 109. †† Spikelets awned. ⊙ _Awns bristle-like and terminal on the paleæ: flowers about six in each spikelet. Leaves setaceous. Panicle secund._ ≡ _Awns long and bristle-like. An annual weed._ _Festuca Myurus_, L. ≡≡ _Awns very short, or merely the drawn out points of the paleæ. Perennial._ _F. ovina._ The rare _F. uniglumis_, Soland., and some other varieties may also come here. Some forms of _F. ovina_ are viviparous (see p. 134), and several varieties have to be distinguished. ⊙⊙ _Awns hair-like and dorsal on the paleæ. Flowers two in each spikelet. Annual, six inches or less in height._ _Aira præcox_, L. The rare _A. canescens_, L. also comes here: its awn is jointed and with a minute tuft of hairs about the middle. (ii) _Panicle lax and open, the fine hair-like branches spreading widely during florescence, or even pendent or drooping._ * Spikelets awnless. † A small aquatic grass with prostrate habit and two-flowered spikelets with broad truncate glumes and paleæ. _Catabrosa aquatica_, Beauv. (Fig. 4). The two-flowered spikelets distinguish it at once from _Glyceria aquatica_, to say nothing of its softer and smoother texture and small stature. _Poa trivialis_ may have two flowers, but it is an erect meadow-grass, with keeled and pointed glumes and paleæ. _Aira_ and _Agrostis_ are awned, or differ entirely in habit. †† Spikelets with at least three or four, but usually more flowers. ⊙ _A perennial field-grass with few large, compressed, bluntly triangular or ovate spikelets, dangling at the end of capillary branchlets; with membranous, loosely imbricated, concave and inflated paleæ and glumes, and 6-8 flowers._ _Briza media_, L. The much rarer _B. minor_, L. is an annual and smaller. ⊙⊙ _Spikelets small and numerous, more or less elongated and pointed, not dangling: glumes and paleæ not inflated_. _Poa_ and _Festuca_ (see p. 116) are difficult genera for the beginner; several of the species vary considerably in detail. Generally speaking the spikelets of _Festuca_ are hard, harsh and sharply pointed, or with short or evident awns; in _Poa_ they are softer, and with blunter points, and never awned. The most obviously awned species of _Festuca_ have more or less setaceous leaves and contracted inflorescences (see p. 111). Some of the mountain species of _Poa_ are extremely variable in small characters. ≡ _Reed-like aquatic, with obtuse glumes rounded dorsally; the large richly branched panicle bearing numerous 5-10 flowered spikelets. Sheath entire or nearly so. No we to the paleæ._ _Glyceria aquatica_, Sm. For other reed-grasses, see note, p. 103. _Glyceria fluitans_ has a more contracted panicle and usually more flowers in the spikelet &c. (see p. 111). ≡≡ _Meadow and pasture grasses &c., usually small. Glumes more or less keeled and acute. Sheaths split_. +Poa.+ ‡ _Spikelets very small and containing 2-3 flowers only. Stem slender, terete and rough; ligule long and acute, palea with prominent lateral nerves._ _P. trivialis_, L. The flowers are fewer than in any other _Poa_, and may be only two. _P. nemoralis_, with 3-5 flowers, may also occasionally be found with two only: it differs from others in its more acute glumes, smooth stem and short ligule. _P. pratensis_ differs in its creeping stolons, short ligule and more numerous 4-5 flowers, and in the indistinct nerves of the palea. ‡‡ _Spikelets 4-6 flowered._ ≡ _Annuals, about six inches high, with relatively large and numerous spikelets for so small a panicle. No “web” at the base of the paleæ._ _P. annua_, L. This is the small grass so common as a weed on road-sides and on lawns, flowering even in winter. For other annual species of _Poa_--_P. rigida_, _P. loliacea_ and _P. procumbens_--see note p. 108 and p. 111. ≡≡ _Perennials._ Δ _With creeping stolons._ _x Stems and leaf-sheaths flattened. Panicle somewhat close and secund, some spikelets being nearly sessile._ _P. compressa_, L. _xx Stems and leaf-sheaths terete. Panicle spreading widely._ _P. pratensis_, L. ΔΔ _Without creeping stolons. Stems and panicle slender, round. A shade-plant._ _P. nemoralis_, L. The rarer species of _Poa_ are _P. bulbosa_ with the stems swollen below; _P. alpina_, also slightly bulbous and often viviparous; _P. laxa_ an allied Highland species; and _P. distans_ a maritime form allied to _P. maritima_ (see p. 111). ** Spikelets with awns or with sharp terminal points (awn-points) to the glumes or paleæ. In some species and varieties of _Festuca_ awns are not evident (see p. 116): the hard paleæ simply end in acute or acuminate points, but these are sharp and in most cases much more so than in any _Poa_. When not so evident, the student will probably think the specimen is a _Poa_ and the flora must be consulted. The difficulty is most likely to occur with varieties of _F. ovina_ and _F. elatior_: in the former the leaves are narrower, setaceous and stiffer than in any _Poa_. The ribbing of the leaf, the ligule, and other characters of the vegetative organs (see pp. 45 and 50) will help in these doubtful cases. † Awns terminal, or sub-terminal; often very short or nearly obsolete and the paleæ merely drawn out at the tips to a hard sharp awn-point. ⊙ _Awns long and sub-terminal, inserted between the teeth of the cleft apex of the paleæ. Sheaths entire. Panicle usually nodding._ +Bromus.+ With the exception of _Festuca Myurus_ and one or two other rare Fescues with setaceous leaves, _Hordeum_ and _Brachypodium_ are the only other genera with awns much resembling the Bromes. The former has a totally different inflorescence, and in the latter the spikelets are practically sessile (see p. 107). ≡ _Spikelets short and fat, and relatively heavy. Paleæ broad and distinctly nerved. Awns fine, about as long as the paleæ._ _B. arvensis_, L. There are several varieties, of which _B. secalinus_ with a looser panicle, and _B. mollis_ with a more compact panicle and very downy, are the chief. ≡≡ _Spikelets lanceolate and with conspicuous awns. Nerves on the paleæ obsolete._ _x Panicle conspicuously loose and drooping and awns long, paleæ narrow and elongated._ _z Sheaths with long often reflexed hairs. A shade-grass over three feet high._ _B. asper_, Mull. _zz Sheaths downy. A weed of open lands and hedges, two feet or less._ _B. sterilis_, L. _B. giganteus_ is rarer than _B. asper_ and has smaller spikelets and more slender awns. _B. maximus_ and _B. madritensis_ are rare. ⊙⊙ _Awns, if present, merely the points of the paleæ, very short or obsolete. Sheaths split: ligule short._ +Festuca.+ ≡ _Leaves flattened. Panicle somewhat close. Often tall grasses._ _z Meadow-grass, with 5-6 to a dozen or more flowers in the spikelet._ _F. elatior_, L. _zz Shade-grass, with 4-5 flowers only in the spikelet._ _F. sylvatica_, Vill. ≡≡ _Leaves subulate or setaceous, at least below. Mountain pasture grass, usually small._ _F. ovina._ Concerning difficulties between _Poa_ and the awnless forms of _Festuca_, see p. 114. _F. elatior_ and _F. sylvatica_ are practically awnless, the awn-points being merely the acuminate tips of the paleæ. The long-awned species of _Festuca_ have compact stiff panicles and narrow or setaceous leaves (see p. 111). Regarding varieties of _F. ovina_, see p. 112. †† Awns, twisted below and bent above, inserted into the middle of the back of the bifid palea or below it. ⊙ _Awns long and conspicuously projecting from the spikelet, which is gaping and contains 3-5 flowers. Leaves flat._ +Avena.+ ≡ _Tall annual corn-weed, with large (18-20 mm.) heavy, pendent, hairy spikelets on the long slender stalks of the lax open panicle. Leaves glabrous._ _A. fatua_, L. This is the so-called Wild Oat, and the type of this group. ≡≡ _Tufted perennials with spikelets more or less erect on stiffer stalks, the panicle therefore less open._ _z Panicle nearly simple; spikelets silvery or reddish, 12-15 mm. long._ _A. pratensis_, L. _zz Panicle branched but not very open; spikelets glistening yellow and only 5-6 mm. long._ _A. flavescens_, L. There is no other genus closely resembling _Avena_. The superficial likeness of some Bromes disappears at once on examination. The spikelets of _Aira_ are much smaller, and the leaves quite different (see below and p. 47). ⊙⊙ _Awns fine and hair-like and not conspicuously protruding from the spikelets; the latter small, 2-5 mm. Flowers two in each spikelet._ +Aira.+ ≡ _Coarse and tall tufted grass with flattened, harsh, and conspicuously ribbed leaves: the very short awns hardly protruding._ _A. cæspitosa_, L. No other grass can be confused with this if the very high ridges of the leaves are observed (see p. 47). ≡≡ _Small grasses with setaceous or very narrow inrolled leaves. Awns slightly protruding._ _x Palea distinctly bifid at the apex: awn nearly twice its length. A very small grass about six inches high: leaves subulate, fine and short._ _A. caryophyllea_, L. _xx Paleæ almost imperceptibly bidentate: awn not much longer than palea. About 12-18 inches high: leaves inrolled._ _A. flexuosa_, L. Other species of _Aira_, with more condensed inflorescences, are dealt with on p. 112. _Agrostis_ is distinguished by the leaves and one-flowered spikelets (see p. 104). _Poa_ and _Catabrosa_ have no awns. CHAPTER VIII. THE FRUIT AND SEED. The stigma of an ordinary grass consists of two divaricating plume-like structures composed of thin-walled cells. When the paleæ open these stigmatic plumes protrude, one on either side, and readily catch pollen shed from the dangling stamens and carried by the wind, and since the pollen of the same flower is usually shed at a time when the stigmas of many neighbouring plants are mature, there is every opportunity for cross-fertilisation. (Fig. 33.) In some cases, however, e.g. _Anthoxanthum_, _Alopecurus_, the flowers are proterogynous, the stigmatic plumes being ready for pollination some time before the pollen is shed from the anthers of the same flower; whereas in most of our grasses the pollen begins to scatter before the stigmas are ready (protandrous). Among exotic grasses, many are diœcious or monœcious--i.e. the flowers contain stamens only or ovary only, on each plant, or on different inflorescences of the same plant respectively--and even in our own _Holcus_ and _Arrhenatherum_ this state of affairs is partially represented, since one flower of the spikelet is male only. In some grasses, e.g. Rye, however, it appears improbable that cross-fertilisation ever occurs, since the paleæ do not open, and the pollen falls on to the stigma direct; and in _Leersia_ and the foreign _Amphicarpum_ the spikelets are completely cleistogamous, those of the latter being on stalks close to the ground which push the flowers into the soil, where pollination and fructification are accomplished. Hybrid grasses are by no means uncommon. To say nothing of the numerous cross-bred Wheats and Barleys, artificial hybrids have been raised between Wheat and Rye. In the Maize an astonishing number of selected cross-breeds have been obtained, and, among others, certain forms in which the seeds have a violet outer layer and a sugary endosperm, are found to transmit these characters to the resulting seed of a variety which would normally have produced seed with white outer layers and starchy endosperm, if the pollen of the former is used on the stigma of the latter. Such direct influences of the pollen are termed _Xenia_. [Illustration: Fig. 37. Pollen-grains adherent to the papillæ of the stigma, on which they germinate, sending the pollen-tubes down between the cells. Kerner. × about 100.] When the pollen-grain, having adhered to the hairy stigma, has begun to germinate, the resulting pollen-tube creeps down between the cells of the stigma, and hands over its enclosed nuclei to the embryo-sac, where fertilisation of the egg-cell is accomplished, by the fusion of one of the pollen nuclei with the nucleus of the egg-cell. As the resulting embryo developes, the sac becomes filled with endosperm-cells charged with starch-grains or sugar, and in the ripe seed the embryo is always found affixed laterally and below to this endosperm--a point of distinction from Sedges, where the embryo is buried in the endosperm. The ripe seed fills the ovary, and its outer walls usually fuse with those of the carpel, forming the well-known _Caryopsis_ or “grain.” [Illustration: Fig. 38. Longitudinal median section of the caryopsis of a grass--e.g. _Lolium_ (× about 35). _p_, pericarp; _t_, attachment to axis; _m_, position of micropyle; _E_, endosperm; _A_, its aleurone layer; _l_, folded leaves of plumule; _r_, radicle; _r´´_, secondary roots; _RC_, root-cap; _s_, scutellum. The dark line _e_ represents the surface where the face of the scutellum is applied to the endosperm and where absorption of the latter takes place.] If such a “grain” is carefully examined, three chief parts are visible in addition to the embryo. (Fig. 38.) Firstly, we find on the outside the fused seed- and fruitcoats, differing in the number of layers and in the microscopic characters of the cells, some of which characters can be employed in diagnoses. (Fig. 39.) Secondly, the great mass of the “grain” internally is composed of delicate cells filled in most cases with starch-grains, the sizes, shapes and arrangement of which can also be employed for diagnoses--e.g. the compound grains of the Aveneæ and Festuceæ are different from the simple polyhedral or rounded grains of the Andropogoneæ and Maydeæ, and some races of Maize have sugar and soluble starch instead of grains of the latter. [Illustration: Fig. 39. Transverse section (highly magnified) through a grain of _Brachypodium pinnatum_ taken about half-way up. 1, epidermis; 2, pericarp; 3, remains of the true seed-coat; 4, vascular bundle; 5, remains of nucellus; _P_, epidermis of nucellus; _G_, aleurone layer: remarkable in being several cells thick; _E_, endosperm. Harz.] Thirdly, the outermost layer or layers of cells of the endosperm are filled with proteids, and are known as the Aleurone layer. (Fig. 38, _A_.) The embryo consists of the folded embryonic leaves in bud (plumule) above, which will grow up on germination as the shoot or “spear,” the short primary root (radicle) below, with in many cases two or more secondary rootlets already showing in its tissues, and from the common “collar” uniting these a more or less prominent shield-shaped organ (scutellum) standing out laterally in contact with the endosperm, the dissolved contents of which it absorbs on germination. (Fig. 38, _s_.) Although typical grasses form a caryopsis as described, exceptions occur. In the exotic _Sporobolus_, _Eleusine_, _Crypsis_ and _Heleochloa_ the fruit becomes truly dehiscent, the seed being loose in the fruit, and the latter opens and allows it to fall out; and in many Bamboos the seed is loose in the _achene_, while in a few cases--e.g. _Melocanna_--the fruit is fleshy and may be as big as a walnut. Returning to the typical grasses. When the fruit ripens in the spikelet, several events may happen. [Illustration: Fig. 40. _Triodia decumbens. a_, “seed,” nat. size; _b_, ditto, × 6. Note the basal hair-tuft and rachilla, and the ciliate, toothed outer palea with a short awn-point, enclosing the inner more delicate palea. Between the two lies the caryopsis. Nobbe.] In most of our grasses the caryopsis comes away trapped between its two paleæ, and the latter bring away with them the small piece of the axis of the spikelet on which they stand: this bit of axis--the _rachilla_--often affords valuable characters in diagnosis. (Fig. 41.) It is the pair of paleæ enclosing their caryopsis which goes by the name of “seed” in most of our grasses. (Fig. 40.) In a few cases, however, e.g. _Panicum_, the spikelet comes away as a whole, so that here the “seed” consists of the glumes, enclosing one, two or more pairs of paleæ with their contained caryopses. Even among our native grasses, however, cases occur where the separation takes place below some of the glumes, and so the “seed,” as met with in samples, consists of glumes as well as enclosed paleæ and caryopsis--e.g. _Anthoxanthum_, _Alopecurus_, &c.--and some care is necessary in examining grass “seed” in these circumstances (see p. 134). [Illustration: Fig. 41. Diagram of a spikelet of a grass--e.g. _Festuca_--comprising six matured flowers and their paleæ, embraced by the two glumes (_g^1g^2_) at the moment of disarticulation as the fruits ripen. The small piece of axis (_a_) left attached to each segment is the rachilla _R_. At _p^2_ the tip of the inner palea is visible protruding from the outer one _p^1_: in the rest it is still enclosed in the latter.] Interesting biological adaptations are met with in the distribution of grass “seeds.” The very small and light fruits of _Agrostis_ easily fall and are scattered by the wind, but in many cases the glumes (_Holcus_) or paleæ (_Briza_) are expanded and serve as “wings” offering extensive surfaces to the wind. In _Arundo_, _Calamagrostis_, _Aira_, &c., fine silky hairs attached to the rachilla serve a similar function, reminding us of the _coma_ of true seeds and the _pappus_ of Composites. In _Hordeum jubatum_ of the prairies, the axis breaks up and the disarticulated portions with their attached tufts of fruits are blown away by the wind, and something similar occurs in our own _H. murinum_ to a less extent. In the exotic _Spinifex_ whole heads of fruits are thus detached and blown over the sands as “tumble weeds.” In _Stipa pennata_ we have an example of perhaps the most complex of all such adaptations: the exceedingly long awn terminating the palea is plumose at the upper end and twisted below, and the hard sharp rachilla at the base of the fruit is furnished with short, stiff hairs directed upwards. The plumed awn serves as a wind surface, the whole fruit flying like an arrow through the air. The stiff hairs below serve to fix the lower end between particles of soil, and by their alternate drying and wetting, the warping of these and of the twisting and untwisting awn drives the sharp base into the soil. (Fig. 42.) Similar mechanisms exist in _Avena_ and others. These bristles and awns also subserve dissemination in other ways, especially by clinging to the wool and fur of sheep and other animals, and cases occur where the twisting awns and reflexed hairs on the hard pointed fruit-base drive the latter into the bodies of sheep with fatal effects--e.g. _Stipa capillata_ in Russia, _S. spartea_ in America, _Aristida hygrometrica_ in New Zealand, _Heteropogon contortus_ in New Caledonia. [Illustration: Fig. 42. Awned fruit of _Stipa_. The reflexed stiff hairs and hard point favour penetration into the soil. The long twisted awn performs hygroscopic movements, and its terminal plume offers surface to the wind. Lubbock.] The driving action of even small reflexed asperities on awns is well illustrated by the fruits of _Hordeum_, which are often made by children to creep up the sleeve. When we come to examine the external features of the “seeds” of grasses--usually the caryopsis enclosed in one or more paleæ, but sometimes in glumes as well--the following diagnostic characters are of importance. The size varies from lengths of 2 mm. or less (_Poa_, _Aira_) (Figs. 43, 44) to 15-20 mm. or more (_Arrhenatherum_) (Fig. 47) and distinction must be made between the various characters of the caryopsis devoid of its coverings (paleæ, glumes) and such as really belong to the latter. The caryopsis proper may be short and stout and devoid of a groove--“Millet-seed” type (Fig. 45)--but is oftener elongated, like a grain of Wheat, and then has the characteristic longitudinal groove on the face opposite that where the embryo is situated (Fig. 46). Details of shape--e.g. cylindroid, fusiform, flattened, &c.--are also of diagnostic value. [Illustration: Fig. 43. _Poa annua. d_, the “seed,” nat. size; _a_ and _b_, ditto, × about 7; _c_, caryopsis, natural size (above) and × about 7. Note the ribs and silky keel. No “web.” Nobbe. Cf. Figs. 54-56.] In many cases the “seed,” consisting of the caryopsis closely compressed between the paleæ, is boat-shaped, e.g. _Lolium perenne_, _Festuca elatior_. If this “boat” is long and narrow it may be termed barge-shaped, e.g. _Brachypodium sylvaticum_, &c. (Figs. 71, 72): if short, broad, and open or shallow, the term coracle-shaped seems to apply, e.g. _Bromus arvensis_ (Fig. 73). [Illustration: Fig. 44. _Aira cæspitosa._ The minute “seed” (nat. size) is seen to the right, and the caryopsis (nat. size) to the left of _c_, the caryopsis, × 8. _a_ and _b_, the “seed,” × 10. The basal awn is about as long as the palea, and the rachilla is very hairy. Nobbe.] [Illustration: Fig. 45. _Phleum pratense._ Millet-seed type. _a_, “seed,” nat. size; _b_, ditto, × about 7; _d_, caryopsis, nat. size; _c_, ditto, × 7. The rounded caryopsis in _b_ is only loosely covered by one palea. Nobbe.] [Illustration: Fig. 46. Boat-shaped “seed” of _Glyceria fluitans_. _a_, nat. size; _b_ and _c_, × about 6. _d_, caryopsis, × about 10. Note the 5-7 strong nerves, and the slender cylindrical rachilla. Cf. Figs. 57 and 58. Nobbe.] [Illustration: Fig. 47. _Arrhenatherum avenaceum._ The “double seed” (_a_ and _b_) consists of two pairs of paleæ with their enclosures. The lower pair (γ) are devoid of fruit, and the outer palea has a long twisted and kneed basal awn: the upper pair (β) enclose the fruit, and the palea has a short straight awn. Note the stiff basal hairs. _a_, nat. size; _b_, × about 6; _c_, caryopsis, nat. size; _d_, ditto, × 6. Nobbe.] [Illustration: Fig. 48. _Lolium temulentum._ Type of boat-shaped “seed” with sub-terminal awn arising from between two teeth. _c_, “seed,” nat. size; _a_ and _b_, ditto, × 6. Note the large smooth rachilla. Nobbe. Cf. Fig. 57.] Further important distinctive characters are obtained from the absence or presence of awns, and the peculiarities--length, stiffness, &c.--of the latter. The awns may be straight, hooked, or kneed (i.e. sharply bent); twisted or not; smooth or serrulate. They may be inserted at the base or near the middle of the back of the investing palea, or glume, or near its apex, as indicated by the terms basal, dorsal, sub-terminal (see Figs. 47-50). Some difficulty arises in connection with terminal awns. In some cases there is a true awn--i.e. a distinct bristle or hair--at the apex of the palea, and apparently continuing its substance without interruption; but in most instances close examination shows that this awn arises from between two minute teeth, and is really inserted at the back of the slight depression between them--e.g. _Lolium temulentum_ (Fig. 48), _Brachypodium pinnatum_ (Fig. 77), &c. In another class of cases the awn appears to be really the prolongation of the palea--e.g. _Nardus_ (Fig. 81), _Festuca Myurus_ (Fig. 80), &c.--and when it runs out into a distinct bristle we may speak of a terminal awn without staying to discuss whether or no it is really terminal in development. [Illustration: Fig. 49. _Agrostis Spicaventi. c_, “seed,” nat. size; _a_ and _b_, ditto, × about 9. The long slender awn is inserted below the bifid tip of the palea. Nobbe.] In _Arundo_, _Cynosurus_ and some Fescues, where the palea tapers off into a stiff long point, I have not spoken of it as an awn, but have described the palea as tapering into a sharp point (awn-point). It must be admitted that the distinction is somewhat artificial, but it has its advantages in practice. [Illustration: Fig. 50. _Bromus sterilis. a_, “seed,” nat. size; _b_ and _c_, ditto, × about 2. Nobbe. Cf. Figs. 80 and 81.] [Illustration: Fig. 51. _Festuca sylvatica. a_, “seed,” nat. size; _b_ and _c_, ditto, × 8. Nobbe. Cf. Fig. 78.] The rachilla (Fig. 41), when present, often affords good characters, and in a few cases is relied on for the distinction of “seeds” otherwise much alike--e.g. _Lolium perenne_ and _Festuca elatior_; and similarly with the presence or absence of hairs (_Digraphis_, _Arundo_, &c.) or “web” (_Poa_) at the base of the “seed.” (Figs. 55, 69.) On germination the primary root of the embryo usually emerges and at once plunges into the soil, but soon ceases to grow, and the secondary roots (and subsequently adventitious rootlets from the lower internodes) soon give the peculiar fibrous character so well known in grass-roots. The plumule either pushes out from the same end of the caryopsis as the root (e.g. Wheat, Rye) or drives its way between the coats to the opposite end (e.g. Barley) and appears as a pointed cylinder of rolled leaves (the “spear”) the outermost of which is sheath only, no lamina being developed. As Darwin showed, the pointed apex of such a plumule is hardened, facilitating the piercing of the soil above, and when the blade attains the open air it performs spiral movements during growth, indicating that similar attempts to rock from side to side have aided the plumule in forcing its way through the soil. It has also been shown that the apices of roots and plumules are sensitive to differences of temperature, of light-intensity, moisture and contact, all of which aid the seedling in establishing its position in the soil and in liberating the “spear.” For particulars the student should read Darwin’s _Power of Movement in Plants_. With regard to the established seedlings of grasses, many interesting details of structure are to be found in them. I have not sufficient material to draw up a diagnostic arrangement of grass-seedlings, but it is evident that such could be done. It may be useful to illustrate this by the following tabular view of the characters of the larger seedlings of our common cereals, in part adapted from Vesque and Percival; though I find that some variations may occur, especially in the development of the auricles. SEEDLINGS. I. First expanded aerial leaves broad, bright green, with 18-24 ribs. _Barley._ The blade tends to twist to the left: auricles, when well developed, long, pointed, and claw-like, embracing the glabrous sheath in front. Ligule long, membranous, pointed and irregularly toothed. The plumule emerges at the upper end of the grain, and the embryo has 5-6 secondary roots. II. First aerial leaves narrower, with not more than 11-13 ribs. A. _Ligule long, rounded and toothed._ _Wheat._ The blade tends to twist to the left: auricles filiform and embrace the densely pubescent sheath. Leaves green. Embryo with three roots. B. _Ligule short and toothed. Leaves with a reddish cast._ (_a_) Blade and sheath softly hairy, the latter with scattered long hairs, the former tending to twist to the left. _Rye._ The first leaf-sheath purple. Auricle-claws more triangular and smaller than those of wheat, and the accompanying bristles are fewer and shorter. Embryonic roots four. (_b_) Blade and sheath glabrous or merely ciliate or silky, the former tending to twist to the right. _Oat._ Auricles filiform. The plumule emerges above. The embryo has three roots. A curious phenomenon is observed in some grasses growing in high latitudes, or mountainous regions, or in moist situations. The flowers, or even entire spikelets, grow out into minute leafy buds, with rudimentary roots at the base, and fall off like the bulbils of other monocotyledons, taking root directly in the damp soil. The phenomenon must be looked upon as a case of apogamy, since the development of sexual organs is entirely passed over; the parts which would normally have become ovary and stamens being transformed into leaves. In some species or varieties--e.g. _Poa alpina_, _Festuca ovina_--this viviparous condition may coexist with normal flowers and spikelets; in others--e.g. _Poa laxa_, var. _stricta_--only the viviparous state occurs. In the following arrangement the student should note that the terms “Seed” and “Fruit” are used in the ordinary sense of the farmer and seedsman: by the former is meant the “seed” as it comes in samples into the market, when the true fruit or grain (_Caryopsis_) is almost invariably invested by adherent “chaff”--i.e. paleæ or glumes or both. When the word Caryopsis is employed, I mean it strictly in the botanical sense explained above. In _Hordeum_, for example, we never see the true fruit, the grain consisting of the caryopsis with paleæ so closely adherent to it, that we are apt to take them as part of the grain itself. The true seed, in the strict botanical sense, is never seen as a naturally separate organ in our native grasses; and, as already explained, only very few exotic grasses ever shed it--e.g. _Sporobolus_. CHAPTER IX. CLASSIFICATION OF GRASSES BY THE “SEEDS” (GRAINS). +I. “Seed” rounded (Millet-seed[12] type). Caryopsis ovoid or sub-globose, devoid of distinct groove, and distending the awnless paleæ, or falling out free.+ +A. Glumes cuspidate, “fruit” yellowish.+ _Phleum pratense._ The student should familiarise himself with the “seed” of _Phleum pratense_, as a type, and an important grass easily obtained pure, but sometimes with minute round seeds of weeds intermixed. _Phleum pratense_, L. (Fig. 45). Palea 2·3 mm. long, five-ribbed, with a short point, delicate but hard, smooth, with a silvery lustre. Inner pale two-nerved. Closely investing the yellow-brown caryopsis, which easily falls out and is ovoid-acute, about 2 mm. long by 1 broad, and finely punctate. The much rarer _P. arenarium_ and the very rare _P. Bœhmeri_ and _P. asperum_ also come here. _Phleum_ is not easily confounded with any other of our grasses, and _Briza_ and _Glyceria_ are almost the only other common grasses of about the same size of which the caryopsis often falls free from the palea (“naked fruits”). _Glyceria_ is longer and corn-shaped, and _Briza_ usually larger. _Anthoxanthum_ and _Phalaris_ are easily distinguished. _Agrostis_ is smaller and “corn-shaped.” Certain species of _Panicum_ present resemblances, but the enveloping paleæ, &c. are very different. _Melica_ also occurs as “naked fruits,” but is rarely seen, and its colour and brilliant lustre distinguish it. +B. Glumes not cuspidate. “Fruit” not yellow.+ (_a_) “Fruit” white, owing to the closely investing palea. _Milium effusum._ A common grass, but not often met with in “seed” grasses. It is eagerly eaten by birds. _Milium effusum_, L. (Fig. 52). Palea about 3 mm. long, with few nerves, closely investing the caryopsis: the seed is ellipsoid-acute, slightly compressed, and 2·2-2·7 mm. long. The inner pale becomes hard and shines like porcelain. (_b_) “Fruit” dark-brown shining; slightly flattened and grooved. +Melica.+ [Illustration: Fig. 52. _Milium effusum._ “Seed,” _a_, nat. size; _b_ and _c,_ × 7. Nobbe.] _Melica_ is rarely met with as “seed.” When it is, it has to be distinguished from the other “Millet-seed” types which readily fall as naked fruits--see _Phleum_, _Milium_, &c. _Agrostis_, _Glyceria_ and other corn-shaped “seeds” are easily distinguished. _Melica nutans_, L. (Fig. 53). “Seed” coracle-shaped. Palea broad, parchment-like, elliptic convex, 5-6 mm. long, 5-7 nerved and keeled, awnless, loose, purplish. Caryopsis ellipsoid-acute, 2-3 mm. long, and easily separating, wrinkled, dark shining brown as if lacquered. [Illustration: Fig. 53. Coracle-shaped “seed” of _Melica nutans_, showing the broad, ribbed and keeled palea (_c_), and small rachilla (_d_). _a_, the “seed,” nat. size; _c_ and _d_, ditto, × 8; _b_, the caryopsis, nat. size; _e_ and _f_, ditto, × 10. Nobbe.] _M. uniflora_, Retz. is commoner and very similar, but neither is often met with in “seed” grass, except as impurities among Fescues. The rare _Panicum Crus-galli_ and allies, and the rice-like _Leersia oryzoides_ as well as _Cynodon Dactylon_, come here. Panicums may occur in grass “seed” from America: Burchard describes them in detail. +II. “Seed” long (Corn and Barley type). Caryopsis oblong or flattened, usually trapped between the boat-shaped paleæ: if otherwise, with an awn.+ +A. “Seed” awnless. There may be a short sharp point to the palea (mucronate), but no prominent hair-or bristle-awn exceeding half the length of the palea.+ (_a_) A “web” or tuft of hairs at the base or on the rachilla. (1) _Hairs of basal tuft silky and erect._ * Pencil of hairs as long as palea or longer. _Calamagrostis lanceolata_, Roth. Palea 3 mm. long, thin, two-toothed and with a short bristle at the apex. Other species of _Calamagrostis_ are awned. None occurs as an ordinary impurity in “seed.” _Arundo Phragmites_, L. Palea narrow and long, 10-11 mm., delicate, entire, tapering to an acuminate point, violet, three-nerved, smooth. Caryopsis about 2 mm. A pencil of long silky hairs on the rachilla. The long acuminate point is almost an awn. _Calamagrostis_ also has long basal hairs: both are useless grasses agriculturally. For _Glyceria_ see note, p. 146. _Avena_, _Aira_ and _Psamma_ are easily distinguished. ** Pencil of hairs short. † _Palea mucronate, 11-12 mm. long: caryopsis 4·5 mm._ _Psamma arenaria._ _Digraphis_ differs in the stout caryopsis, smaller size, double hair-tuft. _Arundo_ has a long pointed palea and long silky basal hairs and is larger. _Psamma arenaria_, Beauv. Palea 11·5 mm. ovate-lanceolate, papery, 4-5 nerved, as rolled round the fruit about 1·3 mm. diameter, yellow, and with a small tuft of stiff fine hairs at the base. Mere trace of awn, sub-terminal. Fruit 4-5 mm. long, obovate, pale-brown. A shore-grass, not often seen as “seed”: more valuable as a sand-binder than as fodder, though the young shoots are grazed. †† _Palea acuminate, and only about 4 mm. long: caryopsis 1·4 mm._ _Digraphis arundinacea._ A Fen-grass, but coarse and not in use except the young growth, and for thatching. _Digraphis arundinacea_, Trin. Paleæ ovate-lanceolate, nerveless and awnless, but silky with double basal hair-tuft, and polished at the base; smooth, hard and shining, and closely investing the caryopsis which has no groove. Dark grey in colour. The glumes are without awns or wings, and are left behind. The allied _Phalaris canariensis_ has wing-like keels to the glumes. _Triodia_ also comes into this group, with short basal hairs; but its broad ciliate palea, 6 mm. long, has a short mucronate point between two teeth (Fig. 40). (2) _Hairs at the base forming a fluffy “web.” Paleæ thin, 2-3 mm. long._ _Poa pratensis._ _P. trivialis._ _P. compressa._ _P. nemoralis._ The “seeds” of _Poa_ proper are nearly all small--not more than 3-4 mm., more or less lanceolate, with tough, keeled glumes, and when “webbed” tend to adhere together as if stuck with cobweb. The keeled glumes give them an angular appearance--triangular in section--and make them tend to lie on the side. Rachilla evident. Nerves of paleæ distinct. _Poa pratensis_, L. (Fig. 55). “Seed” 2-3 mm. long, brownish: caryopsis about 1-1·5 mm. Outer palea acute, indistinctly 3-5 nerved, edges and keel, silky; margins overlapping the hyaline inner palea. The “web” looks like hyphæ of a mould. Caryopsis ellipsoid-acute, with traces of the stigma. It falls easily. No distinct groove, section somewhat triangular. Rachilla truncate. [Illustration: Fig. 54. _Poa nemoralis. c_, the minute “seed” (to the right) and caryopsis (to the left) nat. size. _a_, the “seed,” × 8; _b_, the caryopsis, × 8. Traces of a basal “web,” not shown here, occasionally occur. Nobbe.] [Illustration: Fig. 55. _Poa pratensis._ Type of a “webbed seed.” _a_, “seed,” × about 7; _b_, caryopsis (inverted), × 7. Between are the same, nat. size. Note the nerves on the palea and the conspicuous “web” at the base _a_. Nobbe.] [Illustration: Fig. 56. _Poa trivialis. a_, “seed,” nat. size and × 8; _b_, caryopsis, nat. size and × 7. Note the conspicuous “web.” Nobbe. Cf. Fig. 43.] _Poa compressa_, L. Palea obtuse, nearly glabrous and nerveless, or faintly 3-5 nerved and with a faint web. It is close to _P. pratensis_. _Poa trivialis_, L. (Fig. 56). “Seed” 2-2·5 mm., and with a bluish or bronzed cast. Caryopsis 1-1·5 mm. Palea acute, distinctly five-ribbed, glabrous, the margin scarcely overlapping. Caryopsis grooved, blunt and more tightly held in the palea. _P. trivialis_ differs from _P. pratensis_ chiefly in the distinct ribs and smoother palea, grooved caryopsis, and bluer hue. _P. nemoralis_, L., hardly differs from _P. trivialis_, but the paleæ are sub-acute, nerves obsolete, and scarcely hyaline at the margins. The “seed” is shorter and more acute, and the colour less pronounced, and with hardly a trace of hairs (Fig. 54). When the basal hairs are absent this should go with _P. annua_, &c. (see p. 146). It is practically impossible to distinguish these species by the “seed.” Care is necessary to distinguish _Kœleria_, which is somewhat larger in size, keeled, compressed and nerved similarly, but is more pointed and curved and paler yellowish white in colour. Hard and devoid of web or hairs. _Aira_ is distinguished by the awn: _Agrostis_ by the very different paleæ and caryopsis. The other Poas are devoid of web, though they may have hairs below, and require very careful examination. The whole group is excessively difficult to deal with in “seed,” and a special study of it is needed, since several species are important, and it forms a type. _b_ No web or pencil of hairs below the “seed.” (1) _Apex of palea rounded, blunt, notched, or at most bluntly pointed, but with no trace of awn-or bristle-tip._ * Palea inflated, round-backed and somewhat winged, membranous. _Briza media._ _B. minor._ _Briza media_, L. Paleæ blunt, 2·5-3 mm., without lateral projections, markedly convex--almost conduplicate; nerves several. Caryopsis ovoid, 1·5-2·5 mm., dark brown. Sometimes called a good grass, but meagre and only found in poor meadows in this country. It should perhaps go with the “Millet-seed” type and should be compared with _Phleum_, _Melica_, _Panicum_, &c. “Seed” seldom met with. _B. minor_ is smaller. ** Paleæ not inflated or winged. † _Paleæ broad, flat and truncate, prominently three-ribbed. Caryopsis 2 mm. long._ _Catabrosa aquatica_, Beauv. Cattle like it, but it only grows in ditches &c. in water-meadows: distinction from _Glyceria aquatica_ easy if the paleæ are examined. †† _Paleæ acute or sub-acute, boat-shaped._ ⊙ _Paleæ and “seed” at least 6-8 mm. long._ ≡ _Rachilla flattened or angular, and tapering below._ _Lolium perenne._ Occasionally awned, and then less easily distinguished from _L. temulentum_. One of our most valuable grasses. It forms a distinct type of boat-shaped “seeds.” _Lolium perenne_, L. (Fig. 57). Palea distinctly five-ribbed, glabrous, oblong-lanceolate, obtuse or sub-acute, awnless, about 7 mm. long. Margins membranous. Inner palea nearly as long, delicate, ciliate. Rachilla short, flattened and angular, tapering below (see _Festuca elatior_). Caryopsis about 3·5 mm. long, obovate, yellowish brown. [Illustration: Fig. 57. _Lolium perenne_ with typical boat-shaped “seed.” _a_, natural size; _b_ and _c_, × about 8. _d_, caryopsis, × 8. The rachilla, in _c_, is broader upwards and flatter than in Fig. 58. Nobbe.] [Illustration: Fig. 58. _Festuca elatior_, var. _pratensis_. Lettering and sizes as in Fig. 57: compare the more cylindrical and slender rachilla. Nobbe.] Although _Bromus mollis_, _Holcus lanatus_, &c. occur as impurities, they are easily distinguished: the real difficulties are with _Festuca elatior_ and _F. pratensis_. ≡≡ _Rachilla cylindrical._ _Festuca elatior._ This is an important grass, and should be thoroughly mastered as a type of the boat-shaped “seed.” This, with _Lolium_, _Agropyrum_, other Fescues, and even some Bromes and Poas, will give trouble until the student thoroughly masters the importance of the minute characters of size, nervature, of the rachilla, awn, palea, &c. _Festuca elatior_, L. (var. _pratensis_) (Fig. 58). Palea ovate-lanceolate, five-nerved, slightly scabrid, with a slight membranous margin and cilia, rounded back, and no awn. 6-7·5 mm. long. Caryopsis oblong-obovate, somewhat flattened, hardly grooved and adhering to the paleæ, about 3-3·5 mm. long. Rachilla cylindrical, smooth. The other varieties of _F. elatior_ cannot be distinguished by the “seed” alone: in my samples _F. elatior_ proper is longer than _F. pratensis_, and both have occasionally a trace of awn. Var. _arundinacea_ has a more acuminate, stiff point. _Festuca pratensis_ has its palea as a rule somewhat more acute than _Lolium perenne_, and the flatter tapering rachilla of the latter is more closely appressed to the palea. The caryopsis of _Festuca_ also tends to adhere to the paleæ. ⊙⊙ _Paleæ and “seed” at most 3-3·5 mm. long._ ≡ _Palea devoid of hairs or keel, notched or blunt, and with no trace of awn._ Δ _Palea hyaline, nerves indistinct. Tips notched or blunt._ _Agrostis alba._ There is occasionally a very short basal hair (awn). _Agrostis_ and _Aira_ will present difficulties to the beginner, not only on account of their small sizes, but also from the variability as regards awns, basal hair-tuft, &c. None are of value, and most of them are weeds. _Agrostis alba_, L. (var. _stolonifera_). Palea enclosing the fruit 1·8-2 mm. long, white, delicate, membranous, with a blunt notched apex and three (or five) nerves: occasionally there is a fine kneed basal awn, not projecting. The glumes may remain attached: the outer has a serrulate keel, and often a violet hue. No awn. About 2-3 mm. Caryopsis about 1·1 mm. long, oblong, yellow, corn-shaped, furrowed, shining through. _A. vulgaris_, L., is a variety with slightly smaller fruits, no awn, and usually three nerves to the palea, but they cannot be distinguished with certainty by the “seed.” Rachilla obsolete. The colour of the glumes may vary considerably and is sometimes yellow. The absence of awn, rachilla, and basal hairs distinguishes _Agrostis_ from _Aira_. ΔΔ _Palea membranous, ribbed, tips scarious._ _Glyceria aquatica._ _G. fluitans._ _Glyceria aquatica_, Sm. Palea strongly 5-7 ribbed, obtuse and scarious, about 4 mm. long. Green with a purple cast. Caryopsis dark-brown, about 2 mm. long. Inner palea punctate. Rachilla slender and cylindrical. _Glyceria fluitans_, Br., is very similar, but longer (6 mm.) and more slender; the palea scabrid with truncate or ragged tips, and the inner palea not punctate. Yellow. (Fig. 46.) _Glyceria aquatica_ and _G. fluitans_ are sweet grasses of value in water-meadows only. The “seed” is not often met with. Not only with the Poas, but also with _Catabrosa_ are there difficulties in determination. _Molinia_ and _Kœleria_ also present difficulties with _Glyceria_: the former has fewer and feebler nerves. _Digraphis_ and _Arundo_ are easily distinguished by the basal hairs. ≡≡ _Palea acute and somewhat compressed and keeled, and with hairs on the ribs. Tips nerved._ _Poa annua._ _P. maritima._ _P. distans._ _P. rigida._ _P. loliacea._ _P. bulbosa._ _P. alpina._ Their “seeds” are all small, about 2-3·5 mm. only, and angular, brown, and present many difficulties (see note, p. 141). _Poa annua_, L. (Fig. 43). Palea 3·5 and caryopsis 2 mm. long, so that the “seed” is much larger than _P. trivialis_, and there is no web. Minutely silky-hairy on the keel, and the ribs are strong for a _Poa_. _Poa alpina_, L., has the palea five-ribbed with stiffish hairs below, but no web. Bronzy green-violet. “Seed” 3-3·5 mm. long. Caryopsis 1·5-2 mm., and slightly grooved. It is rare in England, and is interesting as it becomes viviparous in Alpine situations. (2) _Apex of palea distinctly pointed, acuminate or mucronate, but not giving rise to a true, long, bristle-like awn._ * Palea acuminate--i.e. taper pointed. † Not compressed or obviously keeled. _Festuca ovina._ _F. sylvatica._ _Cynosurus cristatus._ It is doubtful whether these should not be regarded as awned: if so they come near _Nardus_--see p. 130. _Festuca ovina_, L. (Fig. 59). Palea rounded on the back, narrow, terete-lanceolate and five-nerved, tip scaberulous and drawn out to a stiff scabrid point half as long as the palea, or less. About 3-4 mm. long without the tip-point, 4-5·5 mm. with it. Rachilla obliquely truncate and concave at its apex. [Illustration: Fig. 59. _Festuca ovina. a_, spikelet, × about 3-1/2. _b_, “seed,” nat. size and × about 7. _c_, caryopsis, nat. size and × 7.] Caryopsis oblong, somewhat flattened, dark-brown. The numerous varieties of _F. ovina_ cannot be distinguished by the “seed”: the allied varieties _F. rubra_, _F. duriuscula_, and _F. heterophylla_, &c. are sometimes more distinctly awned (see p. 172). But difficulties will be found with the whole group, which needs revision. This group comprises the grasses so valued on downs and dry hill-pastures for sheep-feeding. _Festuca sylvatica_, Vill., not a common plant, is also with difficulty separable (Fig. 51). _Cynosurus cristatus_, L. (Fig. 60). Palea canary yellow to light-brown, lanceolate with rounded back and the mid-rib prominent as a slight keel and margins infolded, about 4 mm. long (varies from 3-4·5 × 0·5 to 1 mm. broad), scabrid above, dotted below and acute to acuminate with a scabrid awn-point, often curved. Caryopsis 2-2·3 mm., somewhat flattened. Rachilla short and smooth, dilated above. [Illustration: Fig. 60. _Cynosurus cristatus. a_, “seed” and caryopsis, nat. size; _b_ and _c_, “seed” × about 8. Note the scabrid and slightly curved awn-point. Nobbe. Cf. Fig. 64.] A valuable and easily recognised grass. _Molinia_, _Holcus_ and similar impurities are easily detected: some Fescues are much more like it; e.g. _F. tenuifolia_ (see p. 46) in which the apex tapers suddenly to a point. _Dactylis_ should also be compared. †† Paleæ compressed or distinctly keeled. _Molinia cærulea._ _Kœleria cristata._ Unimportant, except as impurities among other grass “seeds.” _Molinia_ is said to occur as such in samples of _Cynosurus_, _Dactylis, Poa trivialis_, Fescues, &c., but it should give little difficulty except in comparison with _Glyceria_ (see p. 146). _Molinia cærulea_ (Mœnch.) (Fig. 61). “Seed” 3-4 mm. or more, leather coloured or with a bluish tinge. Paleæ divaricating, the lower keeled and compressed, and tapering to a sharp point. Rachilla long, oblique and prominent. Smooth tapering, palea 5·5, fruit 2 mm. long. _Kœleria cristata_, Pers. (Fig. 62). Palea 6 mm., keeled, entire, no awn but stiffly tapering, ribbed, no hairs. Rachilla large. Fruit 4·5 mm. [Illustration: Fig. 61. _Molinia cærulea. a_, “seed,” nat. size; _b_ and _c_, ditto, × about 8; _d_, the caryopsis, nat. size; _e_, ditto, × about 7. Note the compressed, keeled and glabrous palea, and the long slender bone-shaped rachilla. Nobbe.] [Illustration: Fig. 62. _Kœleria cristata. a_, the “seed” (to the left) and caryopsis (to the right), nat. size; _b_, “seed,” × about 7. The palea is compressed and keeled, and, like the large rachilla, glabrous. Nobbe.] ** Palea not taper pointed, but mucronate, or two-toothed, with a sub-terminal point or spine. _Elymus arenarius._ _Agropyrum repens._ _Dactylis glomerata._ _Sesleria cærulea._ _Elymus arenarius_, L. (Fig. 63). Fruiting palea lanceolate, 13-15 × 3 mm., tough and stiffly hairy or velvety: 5-7 ribs. Rachilla stout, hairy. Fruit hairy above, 5-11 mm. × 2·5 × 1·2, somewhat grooved. No keel. Apex of inner palea bifid, outer mucronate. Fruit shelled. Easily distinguished from _Digraphis arundinacea_, which has a basal hair-tuft and very different caryopsis; less easily from _Agropyrum_ and _Lolium_, except in the velvety surface. [Illustration: Fig. 63. _Elymus arenarius. a_, “seed,” nat. size; _b_ and _c_, the same, × 3. Note the stiff, velvety, bifid and mucronate outer palea, and the large hairy rachilla. Nobbe.] [Illustration: Fig. 64. _Dactylis glomerata. a_, spikelet with glumes removed, nat. size; _b_, ditto, × about 6; _c_ and _d_, “seed,” nat. size (below) and × about 6. The stiff and slightly curved awn-point is sub-terminal and arises from between two teeth. Rachilla dilated above. Nobbe. Cf. Fig. 60.] _Agropyrum repens_ may have a mucronate awn-point or not. The small palea 10-12, the caryopsis 5-6 mm. (see p. 169 for description). This troublesome weed (Couch-grass) presents similar difficulties with _Lolium perenne_ that _Agropyrum caninum_ does with _Lolium temulentum_--see p. 168. It is moreover extremely variable. _Dactylis glomerata_, L. (Fig. 64). Stiff awn-point just below the two teeth of apex of pale. Rachilla dilated above. Paleæ 5-6 mm. long exclusive of point, compressed and inflated, ribbed and ciliate-bristly on keel, the tip incurved. Caryopsis yellow-brown, ellipsoid, 2 mm. An important grass, said to be adulterated with _Lolium_, Fescues, _Holcus_, _Molinia_, _Bromus_, &c., most of which should be readily detected. The curved tip is an important distinctive character. _Cynosurus_ and _Festuca arundinacea_, _F. ovina_ and _F. rubra_ present resemblances. The seed is larger than that of _Poa_. _F. ovina_ and _F. rubra_ are smaller, rounded dorsally, and have no keel or cilia: the nerves are less prominent and the rachilla smaller. _Sesleria cærulea_, Ard. Palea distinctly toothed at the apex, making it almost three-lobed and very characteristic; with awn-point; five ribs, serrulate. Fruit grey-yellow, obovate. It is a mountain-and moor-grass of little value. +B. “Seed” awned--i.e. the investing palea bears, or tapers into, a distinct bristle or hair at least as long as itself or nearly so.+ (_a_) Awn not terminal. (1) _Awn stout, either obviously twisted and bent or “kneed.”_ (i) “Seed” consisting of the glumes as well as paleæ investing the caryopsis[13]. ⊙ _Awn bent but not twisted; glumes free below, ribbed, and with stiff short hairs on the keel._ ≡ _Awn sub-terminal, shorter than the palea, hooked._ _Holcus lanatus._ “Yorkshire Fog,” of little use or importance, except that it is frequently found as an impurity of other hairy grasses--e.g. _Alopecurus_. It cannot easily be confounded with any other grass: _Anthoxanthum_ and _Alopecurus_, _Arrhenatherum_, &c. present superficial resemblances only. These glumed hairy “seeds” are uncommon and form an easily recognised type. [Illustration: Fig. 65. _Holcus lanatus_. _a_, “seed”--i.e. complete spikelet--and ditto devoid of glumes, nat. size; _b_, spikelet, and _c_ the same devoid of glumes, × 7. The “seed” is here composed of the keeled glumes enclosing two pairs of paleæ and their flowers (_c_): the upper of these is barren and has a hooked sub-terminal awn to its outer palea. The lower awnless one is fertile. Nobbe.] _Holcus lanatus_, L. (Fig. 65). The “seed” consists of the complete spikelet, separated below the compressed and acute, keeled glumes; these have hairs on the keel, and completely enclose the two flowers and their paleæ. Palea ribless, white to grey, shining, obtuse, that of the upper (male) flower with a sub-terminal short hook-like awn. Total length about 4-5 mm. Caryopsis oblong-ovate, grooved. In its palea about 2-3 mm. long and with a few hairs at the base. ≡≡ _Awn dorsal, kneed, longer than the palea._ _Holcus mollis_, L. (Fig. 66). Palea 2·5 mm., fruit 3·1 mm. long; glumes with stiff hairs or serrulæ on keel. The seeds of _Holcus_ often fall from the glumes, but may bring them away. [Illustration: Fig. 66. _Holcus mollis._ Type of “double seed,” which really consists of the entire spikelet (_a_, nat. size; _c_ and _d_, × 8) comprised of the two glumes enclosing two pairs of paleæ and their enclosures (_b_, nat. size; _e_, × about 8). The lower pair of paleæ are devoid of awns and enclose the caryopsis: the upper pair have stamens only, and the outer palea has a dorsal kneed awn, not twisted or hooked. Nobbe.] _Holcus_ is of little use. The two-flowered spikelets and peculiar awns sufficiently distinguish it among the smaller forms. It is said to occur as an adulterant in “seed” of _Alopecurus_. ⊙⊙ _Awn bent and twisted, basal or nearly so; glumes very hairy._ Δ _Glumes golden brown: one awn straight, one “kneed.”_ _Anthoxanthum odoratum._ The grass which gives the scent to new-mown hay. The “seed” is often impure, containing a continental species _A. Puelii_ and other hairy forms. [Illustration: Fig. 67. _Anthoxanthum odoratum. a_, “seed” and caryopsis, nat. size; _b_, the “seed,” and _c_, caryopsis, × about 7. The “seed” consists of the inner hairy glumes, each with a dorsal awn--one kneed--enclosing the paleæ and caryopsis. The outer pair of unawned glumes has been removed. Nobbe.] _Anthoxanthum odoratum_, L. (Fig. 67). The one-flowered spikelet has four hairy glumes, the outer pair of which are unequal and awnless: the “seed” consists of the inner pair of golden-brown hairy and dorsally awned glumes, covering the thin, membranous, shining, smooth, blunt paleæ and the caryopsis, to which the inner palea adheres. Total length, without awns, about 3-4 mm. Palea 1·6 mm. Caryopsis 1·5 mm., brown, shiny, and easily separating. One awn is short, stiff and straight and inserted above the middle of its glume; the other longer and sharply bent, inserted about the middle. _Hierochloe_, a rare northern grass, also comes here. ΔΔ _Glumes connate below, hairy on the keels._ _Alopecurus pratensis._ _A. geniculatus._ _A. agrestis._ _Alopecurus_ is very characteristic, and should be carefully examined as a type. _A. pratensis_ is a valuable grass and said to be often adulterated with the undesirable _A. agrestis_, _Holcus_, &c. _Arrhenatherum_ and _Avena_ are easily distinguished by the basal hairs, rachilla, &c. [Illustration: Fig. 68. _Alopecurus pratensis. a_, “seed,” nat. size, and _b_, _c_, ditto, × 8; _d_, caryopsis, × 7. The “seed” here consists of the two glumes, connate below and hairy on the keel and ribs, including the caryopsis enveloped in a single palea with a dorsal awn. Note remains of stigma in _d_. Nobbe.] _Alopecurus pratensis_, L. (Fig. 68). Inner palea absent. Outer palea 5 mm., caryopsis 3 mm. long, often with remains of the stigma. The greyish-brown spikelet of _Alopecurus_ easily falls as a whole, included in the glumes; the palea is loose and delicate. Glumes connate below, silky-hairy on keel and ribs all the way up. The palea has a bent dorsal awn, about 5 mm. long. _Alopecurus geniculatus_, L. Palea 2 mm., fruit 1·3 mm. long. The glumes hairy on ribs and keel as in _A. pratensis_: glumes more obtuse. _Alopecurus agrestis_, L. Palea 6 mm., fruit 3 mm. long. Glumes only ciliate, on ribs and keel, except at the base where the hairs are longer. Keel slightly winged. Best distinguished from _A. pratensis_ by the glumes, which are smoother, broader above the middle, harder and with a few basal hairs. The species _A. fulvus_, _A. bulbosus_, and _A. alpinus_ are rare. (ii) “Seed” consisting of the paleæ investing the caryopsis, freed from the glumes. * _Palea at least 14 or 15 mm. long: caryopsis 5-7 mm. [Oat type.]_ _Avena fatua._ _A. pratensis._ _Avena fatua_, L. Palea parchment-like, lanceolate-terete, acuminate and bifid at the apex, rounded on the back and with yellow hairs on the lower part. 15 × 3 mm. Awn brown, twisted and bent, arising from the middle, about 30 mm. long. Caryopsis 7 mm. long, hairy at the top and distinctly grooved. Rachilla with fine bristles. _Avena pratensis_, L. Palea very similar to _A. fatua_, apex 2--4-toothed or bifid, rachilla with stiffer hairs. Caryopsis about 5 mm. long. _Avena pubescens_, Huds. is a variety of _A. pratensis_ found on dry calcareous soils. The caryopsis is very narrow, and the rachilla long and feathered with hairs. “Seed” shorter than _A. pratensis_, 10-13 mm., and darker in colour. _A. fatua_ is an excellent type of the grasses with dorsal twisted and bent awns, and easily examined on account of its size. The student will find difficulties with other species of _Avena_ and _Arrhenatherum_. Harz says the stiff hairs of _Avena_ bring about the formation of intestinal concretions (phytobezoars) and are therefore dangerous to domestic animals. ** _Palea not more than 7-10 mm. long._ † _Caryopsis 4-5 mm. long._ _Arrhenatherum avenaceum_, Beauv. (Fig. 47). Paleæ papery, ribbed. Awn 13-15 mm., twisted below; paleæ, with a tuft of hairs below and a ciliate keel, investing the fruit: the whole being cylindrical, 8-10 mm. × 1·5. Caryopsis 4-5 mm. × 1·2, fusiform, pubescent. Rachilla hairy. The distinctive difference between _Avena_ and _Arrhenatherum_ is in the spikelets as a whole. The latter has the lower flower of each spikelet male only. Samples contain the “double seeds,” and the awn of the upper fertile portion is short (see Fig. 69). †† _Caryopsis not more than 3 mm. long. A tuft of hairs on rachilla and base._ _Avena flavescens._ _Aira flexuosa_, distinguished by its nearly basal awn, harder texture and darker colour of paleæ, and _Dactylis_--awnless and with curved long drawn-out apex--are found as impurities in foreign “seed.” [Illustration: Fig. 69. _Avena flavescens. c_, “seed,” nat. size; _a_ and _b_, ditto, × about 7. The dorsal twisted and kneed awn is very characteristic. Note also the hairy rachilla. The palea is bifid above--not visible in the lateral view. Nobbe.] _Avena flavescens_, L. (Fig. 69). Yellow. Palea about 5 mm. long, five-ribbed, bifid at the apex into two long slender teeth, closely investing the brownish caryopsis, and with a sub-dorsal awn 10 mm. long with little or no twist, and hairy at the base. Rachilla flattened and with white hairs. Caryopsis not much grooved, fusiform, 2-3 mm. long, glumes unequal, somewhat keeled and rough. (2) _Awn dorsal or basal, fine and hair-like, and little or not at all twisted or kneed. “Seed” small._ * A pencil of silky hairs on base or rachilla. Palea bifid at the tip. † _Basal hairs longer than palea, and obscuring the awn._ _Calamagrostis Epigeios._ Of little importance. _Digraphis_ has no awn. _Calamagrostis Epigeios_, Roth. Palea about 3 mm. long with toothed apex and very thin caryopsis 1 mm. A conspicuous tuft of fine silky hairs, longer than the palea at the base and on the rachilla. Awn slender, dorsal, about as long as the palea. _C. stricta_, Nutt. and _C. strigosa_, Hartm. are rare. †† _Basal hairs shorter than palea._ ⊙ _Awn brown, bearded in the middle, thickened and white above._ _Aira canescens._ The student will find considerable difficulties in the various species of _Aira_ and _Agrostis_, owing to their small size and variability as regards awn and basal hair-tufts. All these are weeds, but some occur as adulterants. _Aira canescens_, L. “Seed” (apart from the awn, it is very like _Agrostis_) 1·5-2 mm., with a very thin, smooth, keeled, two-nerved palea, bifid at its apex, through which the yellow caryopsis shines. Awn slender, basal, dark-brown, with oblique colourless hairs above the middle and with a slight swelling above. The palea has a few hairs on its mid-rib below. Caryopsis about 1 mm. long. This grass is somewhat rare in England. The jointed basal awn, with a minute hair-tuft above the middle, is unique, and readily distinguishes it when mixed with _Agrostis_. ⊙⊙ _Awn not bearded or thickened._ ≡ _Palea bifid at apex._ _Aira caryophyllea._ _A. præcox._ _Aira caryophyllea_, L. “Seed” 1·4-1·6 mm., comma-shaped and dark-brown. Palea acute, nerveless, inrolled at edges and with a dorsal, kneed, very fine, dark twisted awn twice as long as the palea: the latter with two-toothed apex and a basal hair-tuft. A common impurity in commercial seed. _Aira præcox_, L. is very similar, and cannot be distinguished with certainty by the “seed,” but has a shorter awn and no basal hairs. Apex of palea two-toothed. ≡≡ _Palea jagged or toothed, but not bifid._ _Aira flexuosa._ _A. cæspitosa._ _Aira flexuosa_, L. (Fig. 70). Palea 5 mm. long, four-toothed at the apex, and caryopsis 2·6 mm. The fine basal awn waved or kneed, about twice as long as the palea. Fruit with a groove. Rachilla hairy. Whole “seed” browner than _Avena flavescens_ (see p. 158). [Illustration: Fig. 70. _Aira flexuosa. a_, “seed,” nat. size; _c_ and _d_, the same, × about 7; _b_, portion of fruiting panicle, showing the flexuous rachis; _e_, the caryopsis, nat. size; _f_, ditto, × about 7. Note the basal hairs and twisted awn. Nobbe. Cf. Fig. 44.] An almost worthless grass, on sandy soils, but important as an impurity in _Avena flavescens_ (see note, p. 158). _Aira cæspitosa_, L. (Fig. 44). The palea, about 2·5 mm. long, toothed above, has a fine straight hair-like basal awn not longer than itself. Caryopsis 1·3 mm., grooved. Rachilla distinctly hairy. Easily distinguished when mixed with _Poa nemoralis_, &c.--e.g. by the awn, hairs on rachilla, &c. It requires scrutiny in regard to _Agrostis_, which also has no awn or basal hairs. ** No basal tuft, or merely a few short microscopic hairs below. Paleæ not bifid above. _Agrostis canina._ _A. Spica-venti._ _A. setacea._ _Agrostis canina_, L., is somewhat larger than _A. alba_. Palea (only one present, sometimes minute) punctate, 2 mm., with a fine dorsal awn a little longer than the palea. Caryopsis 1·2 mm. Rachilla obsolete. The awn is usually absent from _A. alba_ and its varieties; and when present is so small as to be almost negligible. _A. canina_ is easily distinguished from _Poa_ by the rachilla in the latter, and absence of awn. _Aira_ has basal hairs, &c. _Agrostis setacea_, Curt., has the awn basal and just projecting beyond the pointed glumes, and the palea very minute, with a few silky hairs below. _Agrostis Spica-venti_, L. (Fig. 49). Palea 2·4 mm. long, with infolded edges and punctate; a minute rachilla at its base, and a slender awn, 8-9 mm. or more long, inserted below the bifid tip. Caryopsis 1·5 mm. A few silky hairs at the base of the palea. (_b_) Awn terminal or slightly sub-terminal, and straight, or at least not twisted or “kneed.” (1) _Paleæ so closely adherent to the fruit that the terminal awn appears to come from the latter [Barley type]. The three florets generally coherent._ ✲ _Awn at least twice the length of the grain._ _Hordeum sylvaticum._ _H. murinum._ _Hordeum sylvaticum_, Huds. Palea scabrid, ribbed above, awn at least twice as long as the very narrow grain. _Hordeum murinum_, L. Lower palea 9-10 mm. long, five-ribbed, lanceolate and wrapped round and adhering to the fruit (grain), upper palea also ribbed. The grain about 7-8 mm. × 2 × 1·2, hardly grooved. Awn about 30 mm. long, serrulate. Rachilla slightly serrulate. ** _Awn not twice the length of the grain._ _Hordeum pratense._ _H. maritimum._ _Hordeum pratense_, Huds. Spikelet with a reddish tinge; awn almost smooth, less than 20 mm. long: not twice the length of the smooth and obscurely nerved grain. _Hordeum maritimum_, With., similar to _H. pratense_, but softer and the awn somewhat longer. The principal features of the _Hordeum_-grain are the closely adherent paleæ and angular fruit, the stiff awn appearing to come off from it as in _Barley_. The rachilla remains. They are all weeds of no use in agriculture, though _H. pratense_ is not uncommon in good pastures. (2) _Palea investing the caryopsis, often closely, but not fused with it, and its tip and awn quite free._ * Awn not strictly terminal but sub-terminal, or arising from between two teeth or in a sinus at the apex of the palea. † Caryopsis thin, flattened and usually 6-10 mm. long, and the paleæ hairy. ≡ _Palea inrolled, terete-lanceolate-acuminate, or linear-lanceolate (barge-shaped). Apical teeth minute and pointed._ Δ _Palea scaberulous or hairy, awn from half to about its own length._ _Bromus erectus._ _B. asper._ _Bromus erectus_, Huds. [Illustration: Fig. 71. _Bromus asper_, a barge-shaped “seed” with terminal awn, nat. size and × about 5. Cf. Fig. 50. Stebler.] [Illustration: Fig. 72. _Brachypodium sylvaticum_, a barge-shaped “seed” with terminal awn, natural size and × about 5. Cf. Fig. 77. Stebler.] Palea with 5-7 scaberulous ribs, but not hairy, flat above, incurved below, so that the inner palea is clearly visible. About 10-14 mm. long and narrowing somewhat suddenly into the smooth stiff awn, shorter than itself. Indications of a tooth at each side of the base of the awn. Caryopsis somewhat flattened, thin and long, barge-shaped, 8-10 × 1·5-2 mm., pointed at both ends, brown, hairy at the tip with the remains of the stigma. “Seed” often purplish. Rachilla long and slender. Must be carefully distinguished from _Brachypodium_, which has the palea less inrolled and a stouter rachilla. _Bromus giganteus_ has a shorter and flatter “seed” and longer awn. _Bromus asper_, Murr. (Fig. 71). Palea often reddish, 5-7 ribbed and usually roughly hairy, mid-rib scaberulous, about 15 mm. long, linear-lanceolate (barge-shaped), the tip more distinctly two-toothed and tapering more gradually into the smooth awn, about its own length. Rachilla distinct. Otherwise resembling _B. erectus_. _B. giganteus_ has a shorter “seed” and longer awn. ΔΔ _Palea scarcely hairy: awn up to twice its length._ _Bromus sterilis._ _B. giganteus._ _Bromus sterilis_, L. (Fig. 50). Palea nearly smooth, somewhat inrolled, terete-lanceolate-acuminate, tough, red-brown, 12-15 mm. long, seven-ribbed, with a long serrulate awn (20-30 mm. or more) practically terminal. Ribs serrate. Caryopsis 9-10 mm. long, flattened, thin. Rachilla distinct, smooth, much wrapped in, widens upwards and is somewhat flattened. The very slender and long “seed” and caryopsis distinguish this from all but _B. erectus_, which has a shorter awn. Perhaps the awn is truly terminal: if so it should go with _Festuca Myurus_, &c. (see p. 171). The length varies greatly. _Bromus giganteus_, L. Palea 7 mm. long and inrolled, the base and rachilla bristly, indistinctly 5-7 nerved, the tip bifid: sub-terminal awn serrulate, 12-15 mm. long. Caryopsis 4·5 mm. long, flattened, thin, glabrous. The caryopsis is shorter and more ovoid than in other Bromes. ≡≡ _Palea expanded above (coracle-shaped), awn from sinus between two blunt or triangular teeth._ _Bromus arvensis._ _Bromus arvensis_, var. _mollis_, L. (Fig. 73). Palea oblong or obovate, somewhat flattened above (coracle-shaped), distinctly 5-7 ribbed, 8-9 mm. long, not hairy, though the ribs may be ciliate. Awn smooth, arising from the depression between two teeth or rounded projections. Caryopsis flattened and thin, 6 × 1·5 mm.; apt to fall loose from the paleæ. In the variety _B. secalinus_ the awn is usually shorter than the elliptical palea, and originates in the sinus of a notch (Fig. 74): in _B. mollis_ from between two teeth, and is as long as the obovate palea. _Bromus maximus_ and _B. madritensis_ are both rare. The broader nerved paleæ of _B. mollis_ and shorter, fatter caryopsis, as well as the longer awn distinguish it from _B. secalinus_ and _B. arvensis_. In the other Bromes the palea is more inrolled and the “seed” more slender as a rule. The rachilla is usually bent above into a slight kink. The Bromes are an extremely difficult group. The awn is inserted between the two teeth of the palea or just below. The palea smooth or ciliate on the nerves or roughly hairy. The fruit is flattened in the antero-posterior plane, and usually shines through the closely investing palea. A rachilla is visible. In _Brachypodium_ the caryopsis is less flattened, and the apex tapers into the awn without teeth. In _Lolium_ and _Agropyrum_ the caryopsis is still more wheat-like and grooved. [Illustration: Fig. 73. _Bromus arvensis_, var. _mollis_. _a_, “seed,” nat. size; _b_ and _c_, the same, × 3. _d_, caryopsis, × about 3. The awn originates between two teeth of the strongly ribbed palea. Coracle-shaped type. Nobbe.] [Illustration: Fig. 74. _Bromus arvensis_, var. _secalinus_. _a_, spikelet, _b_ and _c_, “seed,” nat. size; _d_ and _e_, the same, × 6. Nobbe. Cf. Fig. 73.] All our Bromes are weeds, but some of them are important adulterants, requiring careful examination. _B. inermis_ is cultivated, and is a valuable grass. Awn short or wanting. Paleæ strongly 5-7 ribbed, inner with a marked central rib, closely adhering to caryopsis. _B. Schraderi_ is also said to be valuable. †† Caryopsis not thin and flattened, corn-like, 3·5-5 mm. Palea smooth, inflated, boat-like. _Lolium temulentum._ A weed of cultivation, said to be poisonous to cattle, a possible explanation of which may be found in a fungus recently discovered as a very constant inhabitant of the tissues under the seed coats. _Lolium temulentum_, L. (Fig. 48). Palea ovate, 6-7·5 × 2·5 mm., papyraceous, inflated, smooth, the tip dry and emarginate with a slender sub-terminal awn its own length or longer. It tends to adhere to the fruit. Fruit 3·5-5 mm. × 2·5 × 1·5, somewhat depressed. Rachilla large, cylindrical and smooth. _L. perenne_ has no awn, or the merest trace of one. “Seed” 10-12 mm. long. Boat-shaped. Palea yellow, three-nerved, margins papery. Rachilla flat, see p. 143. ** Awn terminal, and with no evident teeth at its base. ≡ Palea not much inrolled, ovate-lanceolate to linear-lanceolate, and therefore boat-or barge-shaped. Δ _Very hairy._ _Brachypodium sylvaticum_, Beauv. (Fig. 72). Palea ribbed and hirsute much like that of _Bromus asper_, but straw-coloured, shorter (10-12 mm.), linear-lanceolate, more boat-shaped, and tapering without teeth into the longer (10-13 mm.) hairy awn. Caryopsis 7-8 mm., less flattened than in _Bromus_, with a shallow groove. Rachilla smooth. _B. pinnatum_ (p. 171) has a much shorter awn, and is nearly glabrous. These grasses are weeds, but are said to occur frequently as adulterants. ΔΔ _Glabrous or nearly so._ ++ _Palea five-nerved, pubescent._ _Agropyrum caninum._ _Agropyrum repens_ is also often awned and may be described here (see also p. 150). _Agropyrum repens_, Beauv. (Fig. 76). [Illustration: Fig. 75. _Agropyrum caninum._ Type of boat-shaped “seed” with sub-terminal awn. _a_, nat. size; _b_, × about 9, but with awn cut short. Rachilla thicker above and hairy; palea not toothed. Nobbe. Cf. Fig. 48.] [Illustration: Fig. 76. _Agropyrum repens._ Awned variety. The awn is very short and sub-terminal: the rachilla smooth. _a_, the “seed,” nat. size; _b_ and _c_, ditto, × about 4-1/2. Boat-shaped “seed” with rounded back. Nobbe. Cf. Fig. 57.] Palea tough, 10-12 mm. long, ovate-lanceolate, 3-5 ribbed and smooth; with a short (2-3 mm.) or long (8 mm.) terminal awn or a mere tooth. Rounded back. Fruit grey-brown, ciliate above, 5-6 × 1·4 × 0·7-0·9 mm., depressed, hardly grooved, adhering to the palea. Rachilla smooth or not, and narrowed below. A noxious weed (see p. 150) and hence should be carefully excluded from “seeds.” _A. caninum_, Beauv., has a longer (10 mm. or more) and rougher awn, and is smaller (about 8 mm.), but otherwise very similar. Palea smooth except at the five-nerved apex. Rachilla thickened above, and hairy (Fig. 75). _Elymus_ differs from _Agropyrum_ in its harder velvety palea, no awn, and its club-like velvety rachilla. It is also larger altogether, as a rule. [Illustration: Fig. 77. _Brachypodium pinnatum._ Type of boat-shaped “seed” with awn. _a_, nat. size; _b_ and _c_, × 7. Nobbe. Cf. Fig. 72.] ++++ _Palea seven-ribbed, smooth._ _Brachypodium pinnatum._ _Brachypodium pinnatum_, L., is similar, but the palea more open and boat-like and narrows more suddenly above into the smooth awn which is shorter than itself (Fig. 77). Length 8-9 mm. The caryopsis is, however, much more slender than in _Agropyrum_. For distinction from _B. sylvaticum_, see above. The inner palea is ciliate and more delicate than in _Agropyrum_. ≡≡ Paleæ rolled round the “seed” which is terete and tapering gradually into a stiff awn. Δ _Awn longer than the palea._ _Festuca Myurus._ See also _Festuca ovina_, _Cynosurus_, &c., p. 147, and _Arundo_. _Festuca Myurus_, L. (Fig. 80). “Seed” 5-7 mm. without the long (10 mm.) awn, tapering and slender (like _Nardus_), grey or brown. Finely mamillate upwards. Rachilla small. ΔΔ _Awn shorter than palea._ _Festuca ovina_ (var. _rubra_). _Nardus stricta._ _Aira flexuosa_, _Molinia_ and other moor-grasses occur with these narrow-leafed Fescues, but are easily distinguished: _Molinia_ by having no awn and being shorter and stouter, and _Aira flexuosa_ by the dorsal awn and basal hairs. _Festuca rubra_, L. (Fig. 78). “Seed” pale brown with rosy tinge, 3-5 mm. long without the awn, smooth, or slightly hairy upwards. Caryopsis 2-3·5 mm., compressed, with a shallow broad flat furrow on the ventral face and a median long “hilum.” Rachilla cylindrical, smooth, dilated above. [Illustration: Fig. 78. _Festuca ovina_, var. _rubra_. _a_, “seed,” nat. size; _b_ and _c_, ditto, × about 7. Nobbe. Cf. Fig. 59.] [Illustration: Fig. 79. _Festuca ovina_, var. _heterophylla_. _a_, spikelet, × about 3-1/2; _b_, “seed,” and _c_, caryopsis, nat. size; _d_ and _e_, “seed,” and _f_, caryopsis, × 7. Nobbe.] The variety _F. heterophylla_ has narrower and longer “seeds,” and a hispid rachilla. Palea 5-6 mm.: caryopsis 3·5-4·5 mm. (Fig. 79). Perhaps _Bromus sterilis_ should also come here (see p. 165). With regard to these Fescues the student may note that _F. ovina_, var. _tenuifolia_, has the smallest (4-5 mm.) and most ovoid “seeds,” usually golden brown in colour. _F. rubra_ is darker and larger (5-6 mm.), as is also _F. duriuscula_ (6-7 mm.): the latter is also narrower, with toothed palea, tapering suddenly at the base and more awned. _F. heterophylla_ is much like _F. duriuscula_, but the palea less toothed, and it tapers gradually at the base. The whole group is very difficult, and needs attention. [Illustration: Fig. 80. _Festuca Myurus. a_, “seed,” nat. size; _b_ and _c_, ditto, × about 6. Compare Fig. 50. Nobbe.] [Illustration: Fig. 81. _Nardus stricta._ Type of cylindrical “seed” with a terminal stiff awn, here serrulate; _c_, “seed,” nat. size; _a_ and _b_, ditto, × 8. Compare Fig. 50. Nobbe.] _Nardus stricta_, L. (Fig. 81). Outer palea tough and fused, 10-12 mm. long, narrow, lanceolate and tapering gradually into the stiff, serrulate, terminal awn shorter than itself. Inner palea minutely toothed at the apex and without awn, loosely enclosing the red-brownish yellow to bluish grey fruit which has no groove. “Seed” 4-6 mm. × 0·6 × 0·5 (without the awn), more or less triangular in section and serrulate on angles above. BIBLIOGRAPHY. BENTHAM AND HOOKER, _British Flora_, London, 1896. BONNIER and LAYENS, _Nouvelle Flore de France_, Paris, 1887. BRUNS, _Der Grasembryo_ in _Flora_, 1892, vol. LXXVI. BURCHARD, _Die Unkrautsamen der Klee-und Grasarten_, Berlin, 1900. DARWIN, _Power of Movement in Plants_, London, 1880. DUVAL JOUVE, in _Mémoires de l’Acad. des Sciences de Montpellier_, 1871, vol. VII. FREAM, _Elements of Agriculture_, London, 1892. GROB, in _Bibliotheca Botanica_, H. 36, 1896. GUÉRIN, _Recherches sur le développement du Tégument &c. des Graminées_ in _Ann. d. Sc. Nat._ 1899. GÜNTZ, _Unters. ü. d. anatomische Structur d. Grasblätter_, Leipzig, 1886. HACKEL, in Engler’s _Natürliche Pflanzenfamilien_, II. Th. 2 Abth. 1887. HARZ, _Landwirthschaftliche Samenkunde_, Berlin, 1885. HOLZNER, _Beitr. zur Kenntn. d. Gerste_, Munich, 1888. _Index Kewensis_, London, 1893-95. JACKSON, _A Glossary of Botanic Terms_, London, 1900. KIENITZ-GERLOFF, _Botanik für Landwirte_, Berlin, 1886. NOBBE, _Handbuch der Samenkunde_, Berlin, 1876. PARNELL, _British Grasses_, London, 1845. PÉE-LABY, in _Annales des Sc. Naturelles_, 1898, vol. VIII. PERCIVAL, _Agricultural Botany_, London, 1900. PFITZER, in Pringsh. _Jahrb. f. wiss. Bot._ B. VII. SCHMID, in _Bot. Centralbl._ 1898, B. LXXVI. SCHWARZ, _Forstliche Botanik_, Berlin, 1892. SCHWENDENER, in _Sitzungsber. d. Akad. Berlin_, 1889 and 1890. SETTEGAST, _Die landwirthschaftl. Sämereien u. d. Samenbau_, Leipzig, 1892. SINCLAIR, _Hortus gramineus Woburnensis_, London, 1824. SOWERBY, _The Grasses of Great Britain_, London, 1861. STEBLER and SCHROETER, _The Best Forage Plants_, London, 1889. SUTTON, _Permanent and Temporary Pastures_, London, 1886. TRIMEN, Article _Grasses_, in _Encyclopædia Britannica_, 9th ed. VAN TIEGHEM, _Morphol. de l’embryon &c. chez les Graminées_ in _Ann. des Sc. Nat._ 1897. VESQUE, _Traité de Botanique Agricole &c._ 1885. WARMING, _Lehrb. d. Oekologischen Pflanzengeogr._ Berlin, 1896. WITTMACK, _Gras- und Kleesamen_, Berlin, 1873. FOOTNOTES: [Footnote 1: Some foreign grasses (_Andropogon_, _Panicum_, &c.) have solid stems, and in _Psamma_ and some others the lower parts may be solid.] [Footnote 2: Leaf-stalks occur in tropical Bamboos.] [Footnote 3: Tropical Bamboos branch in the upper parts and are woody. _Dinochloa_ and _Olyra_ are climbing grasses.] [Footnote 4: Except, of course, in cases of virgin ground rapidly occupied by the seedlings.] [Footnote 5: The most marked exceptions are the lemon-scented grasses (especially _Andropogon_) of India and Ceylon.] [Footnote 6: The pale flanking lines seen in many grasses on each side of the mid-rib are the series of motor-cells referred to on p. 25.] [Footnote 7: They may have short microscopic asperities, but there are no distinct long hairs.] [Footnote 8: Very like a Poa when opened out, but the leaves are scabrid at the sheaths.] [Footnote 9: Strictly speaking a spike is an axis bearing sessile _flowers_--not sessile _spikelets_: in Grasses, however, the conventional abbreviated term is sanctioned by long usage. The same applies to the panicle, &c.] [Footnote 10: See note, p. 87.] [Footnote 11: See note, p. 87.] [Footnote 12: This term does not necessarily imply any botanical relationship with the true Millets (_Panicum_), but merely that the caryopsis is short and broad as in these grasses.] [Footnote 13: In cases where the “seed” has fallen from the glumes the sample will usually show some of the latter lying loose.] INDEX, GLOSSARY AND LIST OF SYNONYMS. Figures in bold type (+25+) refer to pages whereon the species or subject is more particularly dealt with; figures in italics (_25_) refer to pages containing illustrations. Achene, 123 Acicular--bristle-like Acuminate--tapering to a long point, 21, 139, 146, 147 Acute--simply pointed, 19, 21 Adaptations, 20, 24, 36, 37, 70, 124, 125, 132 Adventitious roots, 8, 131 Agriculture, 2, 3 _Agropyrum_--Wheat-grass, 11, 14, 22, 25, 26, 36, 49, 50, 51, 57, 69, 88, 90, 91, +106+, 107, 108, 144, 150, 167, 170, 171; _A. caninum_, 7, 21, 28, 34, +57+, +80+, 92, +107+, 150, 168, _169_, +170+; _A. junceum_--var. of _A. repens_, 21, 29, 33, 35, 36, 57, _66_, +81+, 102, 107; _A. repens_, 7, 30, +57+, +80+, 81, 93, 102, +106+, 149, +150+, _169_, +170+ _Agrostis_--Bent-grass, 7, 15, 22, 25, 49, 50, 51, 52, 53, 57, 82, 88, 89, 91, 103, +104+, 105, 112, 118, 125, 136, 137, 141, 144, 145, 159, 160, +161+; _A. alba_, 7, 11, 13, 14, 28, 29, 32, 33, 34, 51, 52, 69, 92, +104+, 144, +145+, 162; _A. canina_, 7, 11, 20, 28, 29, 37, 51, 52, +104+, 161, +162+; _A. setacea_, 31, 104, 161, +162+; _A. Spica-venti_, 31, 104, _130_, 161, +162+; _A. stolonifera_--var. of _A. alba_, 14, +51+, 52, 104, +145+; _A. vulgaris_--var. of _A. alba_, 29, 51, 52, 66, 104, +145+ _Aira_--Hair-grass, 6, 20, 21, 36, 48, 88, 89, 90, 91, 103, 104, 105, 106, 110, 112, +117+, 118, 125, 127, 138, 141, 144, 145, 159, 162; _A. alpina_--var. of _A. cæspitosa_; _A. canescens_, 8, 11, 14, 32, +47+, 66, 78, 91, 112, +159+; _A. caryophyllea_, 8, 10, 14, 29, 32, +46+, +118+, +160+; _A. cæspitosa_, 6, 11, 14, 22, 23, 25, 28, 33, 37, 41, +47+, 48, 63, _65_, 68, 69, +77+, 104, 106, +117+, _128_, 160, +161+; _A. flexuosa_, 7, 11, 14, 29, 33, 34, +46+, 68, 70, _71_, +79+, +118+, 158, +160+, _161_, 171; _A. montana_--var. of _A. flexuosa_; _A. setacea_--var. of _A. flexuosa_; _A. præcox_, 8, 10, 29, 30, 32, +47+, 91, +112+, 160 Air-spaces, 21, 39, 40, 62 Aleurone layer, _121_, _122_, 123 _Alopecurus_, 25, 53, 55, 88, 89, 90, 93, +101+, 109, 110, 119, 124, 152, 153, 155; _A. alpinus_, 31, 101, 156; _A. agrestis_, 7, 18, 30, 50, 52, 53, +101+, 155, +156+; _A. bulbosus_--var. of _A. geniculatus_, 8, _9_, 156; _A. fulvus_--var. of _A. geniculatus_, 156; _A. geniculatus_, 7, _9_, 11, 14, 15, 28, 29, 33, 40, 48, 52, 53, +101+, 155, +156+; _A. pratensis_, 7, 11, 13, 14, _18_, 28, 32, 49, 50, 51, +52+, 55, +82+, +101+, _155_, +156+ Alpine Foxtail--_Alopecurus alpinus_ Alpine Meadow-grass--_Poa alpina_ Alpine Poa--_Poa alpina_ Alps, 36, 37 _Ammophila--Psamma_; _A. arundinacea_--_Psamma arenaria_ _Amphicarpum_, 120 Anatomy, 62-71, 95 _Andropogon_, 4, 27 Andropogoneæ, 122 Animal-distribution of seeds, 125 Animals killed by grasses, 127 Annual Beard-grass--_Polypogon monspeliensis_ Annual grasses, 10, 11, 37, 43, 59, 114 Annual Meadow-grass--_Poa annua_ Anther, _93_, 94, 119 Anthesis--the period of opening of the flower, 96 _Anthoxanthum_--Vernal grass, 11, 13, 22, 26, 27, 36, 56, 58, 60, 83, _87_, 88, 90, 91, 94, 97, 110, 119, 124, 136, 152, _154_; _A. odoratum_, 7, 28, 32, 33, 34, +57+, +76+, +102+, +103+, +154+; _A. Puelii_, 67, 154 Anti-ligular peg, 41 _Apera--Agrostis_; _A. Spica-venti_--_Agrostis Spica-venti_ Apex of leaf, 19, +21+, +22+ Apogamy, 134 Appressed hairs, 65 Aquatic grasses, 27, +28+, 39, 62, 103, 111, 112, 113 Arctic species, 37 _Aristida_, 36; _A. hygrometrica_, 127 _Arrhenatherum_--False Oat, 6, 11, 13, 14, 17, 26, 32, 55, 56, 58, 60, 61, 66, 89, 90, 91, 92, 119, 152, 155, 157; _A. avenaceum_, 6, 8, 25, 28, 33, 34, +56+, 66, +77+, _93_, +106+, _129_, +157+ _Arundo_--Reed, 11, 14, 19, 20, 37, 40, 68, 69, 90, 91, 93, 103, 125, 130, 131, 139, 146, 171; _A. Donax_, 21, 75; _A. Phragmites_, 2, 6, 29, 32, 40, +51+, 55, 66, +75+, +138+ Asperities--minute stiff hairs giving roughness to the touch, 24, 45, 65, 66, 75, 77, 127 Auricles--ear-like projections at base of leaf-blade, 22, 133 _Avena_, _5_, 15, 21, 23, 47, 54, 56, 88, 89, 90, 91, 92, 95, 104, 106, +116+, 117, 125, 127, 138, 155, 157, _158_; _A. alpina_--var. of _A. pratensis_; _A. elatior_--_Arrhenatherum avenaceum_; _A. fatua_, 28, 77, +117+, +156+, 157; _A. flavescens_, 7, 11, 13, _18_, 26, 28, 56, +60+, 61, +81+, +117+, +158+, 161; _A. pratensis_, 7, 11, 14, 20, 21, 22, 25, 27, +47+, 56, 61, 63, 66, 81, +117+, 156, +157+; _A. pubescens_--var. of _A. pratensis_, 16, 26, 27, 32, 33, 56, +61+, 68, +157+; _A. strigosa_--var. of _A. fatua_ Aveneæ, 122 Awn, 91, 92, +95+, 99-118, +125+, _126_, 127, _128_, _129_, +130+, _131_, 142, 144, 151, 153, 154, 159, 160, 162, 163, _164_, 166, _167_, 168, _169_, _170_, 171, _173_ Awned grasses, +92+, 99-101, 102, 103, 104, 105, 106, 107, 111, 112, 113, 114, 115, 116, 117, 151-174 Awned Nit-grass--_Gastridium lendigerum_ Awnless Brome--_Bromus inermis_ Awnless grasses, +93+, 104, 105, 107, 108, 109, 110, 111, 112, 138-151 Awn-point, 114, 115, 116, _123_, 131, _150_ Ballast plants, 30 Bamboos, 1, 5, 6, 37, 38, 96, 97, 123 _Bambusa_, 96 Barge-shaped “seeds,” 128, 163, _164_, 168 Barley--_Hordeum_, 120, 132, +133+, 163 Barley-type of “seed,” 138, 162 Barren Brome--_Bromus sterilis_ Barren flowers, 86, 89, 90, 99, 100 Basal-awn, 92, _128_, _129_, 130, 159 Basal hair-tufts, 138, _158_, 159, 160, 161 Base of leaf, _18_, _19_, 20, 22 Bast-sclerenchyma, 70 Bearded Darnel--_Lolium temulentum_ Bearded Wheat-grass--_Agropyrum caninum_ Beard-grass--_Polypogon_ Bent-grass--_Agrostis_ Bent-grass--_Agrostis canina_ Bermuda grass--_Cynodon Dactylon_ Biennial grasses, 10, 43 Bifid--cleft into two teeth, 95 Bitter-tasting grasses, 58, 59 Blade of leaf, 17, _18_, _19_, 20, 22, _23_, _24_, 26 Blue Moor-grass--_Sesleria cærulea_ Boat-shaped “seeds,” 127, _128_, _129_, 138, 142, _143_, 144, 167, 168, _169_, _170_ Bœhmer’s Phleum--_Phleum Bœhmeri_ _Brachypodium_--False Brome, 11, 14, 20, 60, 70, 88, 90, +107+, 108, 109, 165, 167; _B. pinnatum_, 7, 34, +61+, +78+, 93, +107+, 130, 168, _170_, +171+; _B. sylvaticum_, 7, 26, 28, 33, 34, 60, +61+, 76, 78, 92, +107+, 128, _164_, +168+, 171 Bracteoles, 95, 96, 97 Bracts, 94, 97 Branching, 6, 11 Branching of inflorescence, 83 Bristle-grass--_Setaria_ Bristle-leafed Bent-grass--_Agrostis setacea_ Bristle-like leaves, _16_, 21, _24_, 45 Bristle Oat--_Avena strigosa_ Bristles, 67, 125, 130 _Briza_--Quaking-grass, 14, 16, 22, 25, 90, 91, 92, 104, 136; _B. media_, 8, 11, 17, 27, 32, +45+, 66, +77+, +112+, +142+; _B. minor_, 10, 17, +45+, 112, 142 Brome--_Bromus_, 166, 167 _Bromus_--Brome-grass, 6, 10, 14, 17, 26, 44, 51, 59, 61, 76, 90, 91, 92, 95, 103, 104, 107, +115+, 117, 144, 151, 168; _B. Alopecurus_, 95; _B. arvensis_, 7, 8, 11, 27, 30, 32, +43+, 44, +76+, 108, +115+, 128, +166+, _167_; _B. asper_, 6, 11, 17, 20, 22, 26, 28, 33, 34, +43+, 44, 59, 76, +115+, 116, _164_, +165+, 168; _B. commutatus_--_B. racemosus_; _B. diandrus_--_B. madritensis_; _B. erectus_, 7, 11, 13, 14, +43+, 51, 70, 100, +164+, 165, 166; _B. giganteus_, 6, 11, 28, 33, 34, +43+, 44, 51, 76, 82, +115+, 116, 165, +166+; _B. inermis_, 13, 22, 31, +43+, 167; _B. madritensis_, 31, 116, 166; _B. maximus_, 31, 116, 166; _B. mollis_--var. of _B. arvensis_, 8, 26, +43+, 44, 108, 115, 143, +166+, _167_; _B. multiflorus_--var. of _B. arvensis_; _B. racemosus_--var. of _B. arvensis_; _B. Schraderi_, 167; _B. secalinus_--var. of _B. arvensis_, 115, 166, _167_; _B. sterilis_, 7, 11, 27, 30, 32, +43+, 44, +76+, +116+, _131_, +165+, 172 Brown Bent--_Agrostis canina_ Buds, 12 Bulbous Meadow-grass--_Poa bulbosa_ Bulbous Poa--_Poa bulbosa_ Bulbs, 8, 37, 114 _Calamagrostis_--Small reed, 29, 40, 88, 89, 125, 138; _C. Epigeios_, 31, 70, 78, +103+, +159+; _C. lanceolata_, 31, 66, 103, +138+; _C. strigosa_, 103, 159; _C. stricta_, 31, 103, 159 Canary grass--_Phalaris canariensis_ Carpel, 97, 121 Caryopsis--the true fruit of the grass, _121_, _122_, 123, 124, 127, _128_, 132, +134+, 135 _Catabrosa_--Whorl-grass, 14, 21, 23, 29, 40, 63, 84, 88, 90, 91, 92, 104, 105, 118, 146; _C. aquatica_, _12_, 25, 31, 73, +112+, 142 Cat’s-tail grass--_Phleum_ Cat’s-tail type of inflorescence, 100 Cells, 65 Cereals, 1 Chaff, 85, 134 Chalk-fleeing, 35 Chalk species, 27, +32+, 35 _Chamagrostis_--_Mibora_ Chlorophyll, 2, 62, 70, 72, 73, 95 _Cinna_, 97 Circular shoot sections, _16_, 43 Classification according to anatomical characters of leaf, 72-82 Classification according to floral characters, 97, 99-118 Classification according to characters of seed, 135-174 Classification according to vegetative characters, 39-61 Classification of seedlings, 133 Clay species, 32 Cleistogamous--when pollination and fertilisation are completed in flowers which do not open, 120 Climbing grasses, 6 Close panicle--an inflorescence in which the primary branches do not diverge widely from the rachis, 110 Cock’s-foot--_Dactylis glomerata_, 83 Cockspur Panicum--_Panicum Crus-galli_ Collar, 58, 123 Coloured nodes, 15 Coloured sheath, 18 Coma, 125 Common Cat’s-tail--_Phleum pratense_ Common Dog’s-tail--_Cynosurus cristatus_ Common Foxtail--_Alopecurus pratensis_ Common Mat-grass--_Nardus stricta_ Common Quaking-grass--_Briza media_ Common Reed--_Arundo Phragmites_ Compact Brome--_Bromus madritensis_ Composites, 2, 125 Compressed shoots, 15, _16_, 40, 41, 48, 53 Conduplicate--folded, 15, _16_, 20, 63 Convolute--inrolled, 15, _16_, 63 Copses, grasses of, 28, 34 Coracle-shaped “seeds,” 128, _137_, 166, _167_ Cord-grass--_Spartina stricta_ Coriaceous--leathery, 21 Corn, 1 Corn-field species, 28 Corn-type of fruit, 136, 138, 167 _Corynephorus canescens_--_Aira canescens_ Cotton-grass--_Eriophorum_ Couch-grass--_Agropyrum repens_. _See also_ Twitch, 150 Creeping Fescue--_Festuca rubra_ Creeping grasses, _12_, 13, 14, _15_ Creeping grass-seeds, 127 Creeping Soft-grass--_Holcus lanatus_--_Holcus mollis_ Creeping stem, 12 Crested Dog’s-tail--_Cynosurus cristatus_ Crested Kœleria--_Kœleria cristata_ Cross-breeds, 120 Cross-fertilisation, 119, 120 _Crypsis_, 123 Culms, 14, 37, 83 Curved Lepturus--_Lepturus incurvatus_ Cuspidate--ending suddenly in a short point, 135 Cut-grass--_Leersia_ Cuticle, 68, 70 Cutinized, cuticularized--impregnated with corky substance, 64 Cylindrical inflorescence, 90 Cylindrical “seed,” _173_ _Cynodon_--Dog’s-tooth grass, 14, 65, 67, 69, 87, 90, 105; _C. Dactylon_, _15_, 31, +72+, 137 _Cynosurus_--Dog’s-tail, 14, 18, 25, 49, 50, 52, 81, 88, 89, 90, 93, 103, 130, _148_, 151, 171; _C. cristatus_, 7, 11, 13, _23_, 28, 32, +50+, +80+, +108+, 147, +148+; _C. echinatus_, 100, 108 _Dactylis_--Cock’s-foot, 11, 13, 14, 16, 20, 26, 41, 63, 83, 88, 89, 90, 91, 93, 103, 148, 158; _D. glomerata_, 7, _16_, 17, 27, 32, 33, 34, +41+, 65, 66, 69, +74+, +109+, 149, _150_, +151+ Darnel--_Lolium perenne_--_Lolium temulentum_ Decumbent Heath-grass--_Triodia decumbens_ Dehiscent fruits, 123 Depauperated--starved and consequently dwarfed, 109 _Deschampsia cæspitosa_--_Aira cæspitosa_ _Deschampsia flexuosa_--_Aira flexuosa_ _Digitaria_--_Panicum_ Digitate--spread out like fingers, _15_ _Digraphis_--Reed-grass, 6, 11, 13, 26, 40, 41, 51, 55, 69, 73, 75, 90, 91, 92, 103, 131, 139, 146, 159; _D. arundinacea_, 6, _16_, _23_, 29, 32, +54+, 64, +75+, +103+, +139+, 150 Dimensions of grasses, 6 _Dinochloa_, 6 Diœcious, unisexual, the male and female flowers being on separate plants, 119 Disarticulation of fruits, _124_ Dissemination, 125, 127 Distichous--in two ranks on the axis, 106 Distribution of grasses, 2, 37, 38 Distribution of seeds, 124-127 Distribution of sexes, 119 Ditches, grasses of, 28, 29 Dog’s-tooth grass--_Cynodon Dactylon_ Dorsal awn, 92, 112, 116, 130, 159 Double seed--grass “seed” where the remains of a second flower come away with the first, _152_, _153_ Downs, grasses of, 29 Downy Oat--_Avena pubescens_ Dry leaves, 21 Dry situations, 24, 26, 29 Dry soils, 29, 32 Duration, 10 Dwarfed species, 6 Early Hair-grass--_Aira præcox_ Ears, _19_, 22, 57, 59 _Echinochloa_--_Panicum_ Effects of grasses on soil, 35, 36 Egg-cell, 121 _Eleusine_, 123 Elliptical shoot-section, 16, 44 _Elymus_--Lyme-grass, 6, 13, 14, 21, 22, 25, 36, 48, 57, 63, 65, 69, 79, 90, 92, 102, 170; _E. arenarius_, 6, 29, 33, 35, 36, +48+, 66, _67_, +108+, +149+, _150_ Embryo, 121, 131, 133 Embryo-sac, 121 Embryonic bud--plumule, 123 Embryonic roots, 123, 133 Endosperm, 120, _121_, _122_, 123 Energy stored in leaves, 2, 3 Entire--not cut: with unbroken outline, 19 Entire sheath, 17 Entire-sheathed grasses, 17, 39, 113, 115 Epidermis, 25, 36, 62-67, 70, 76, _122_ Equitant--one folded leaf straddling over another, 39, 41 _Eriophorum_, 3 Extra-vaginal shoots, 12 False Oat--_Arrhenatherum avenaceum_ Female flowers, 89 Fertile flowers, 86, 89, 90 Fertilisation--the fusion of the nucleus of the pollen-tube with that of the egg-cell, 121 Fescue--_Festuca_, 115, 130, 137, 144, 148, 151, 172 _Festuca_--Fescue, 2, 6, 7, 15, 21, 25, 36, 49, 51, 53, 90, 91, 92, 108, 109, 110, 113, 114, 116, _124_, 144, _147_; _F. arundinacea_--var. of _F. elatior_, 144, 151; _F. calamaria_--_F. sylvatica_; _F. duriuscula_--var. of _F. ovina_, 46, _69_, +78+, 80, 147, 172, 173; _F. elatior_, 6, 7, 11, 13, 14, 18, 19, 22, 25, 28, 32, 44, +50+, 51, 63, _64_, 82, _84_, 108, 111, 115, +116+, 128, 131, _143_, +144+; _F. gigantea_--_Bromus giganteus_; _F. heterophylla_--var. of _F. ovina_, 13, 46, 69, 71, 78, 80, 147, +172+, 173; _F. uniglumis_, 31, 92, 111; _F. loliacea_--var. of _F. elatior_, 90, 108; _F. Myurus_, 8, 10, 14, 19, 20, 28, +46+, 90, 91, 92, 99, +111+, 115, 130, 166, +171+, _173_; _F. ovina_, 7, 8, 11, 13, 14, _19_, 20, 22, _24_, 28, 32, 33, 36, +45+, 46, 68, 69, 70, +79+, +111+, 112, 115, +116+, 134, +147+, 151, 171, _172_; _F. pratensis_--var. of _F. elatior_, 7, _19_, _24_, 49, 63, _64_, _84_, 111, _143_, +144+; _F. procumbens_--_Poa procumbens_; _F. rigida_--_Poa rigida_; _F. rubra_, var. of _F. ovina_, 7, 13, 14, 18, _24_, 33, 46, 69, 78, 80, 147, 151, +171+, _172_; _F. sabulicola_--_F. rubra_, 46; _F. sciuroides_--var. of _F. Myurus_, 25, 26, 46; _F. sylvatica_, 6, 11, 14, 28, 34, +116+, _131_, 147; _F. tenuifolia_--var. of _F. ovina_, 46, 148, 172; _F. vivipara_--var. of _F. ovina_ Festuceæ, 122 _Fibichia umbellata_--_Cynodon Dactylon_ Fibrous roots, 8 Fibrous Twitch--_Agropyrum caninum_ Field Brome--_Bromus arvensis_ Filament, 94 Fine Bent--_Agrostis vulgaris_ Finger-grass--_Panicum glabrum_ Fiorin--_Agrostis alba_ Firing, 35, 38 Flanking lines, 41, 53, _63_, 73, 74 Flat leaves, 20, 47, 77 Flat shoots, 15, _16_, 20 Flattened Meadow-grass--_Poa compressa_ Flavour, 27 Fleshy fruits, 123 Floating leaves, 39 Floating Foxtail--_Alopecurus geniculatus_ Floating Meadow-grass--_Glyceria fluitans_ Floating Sweet-grass--_Glyceria fluitans_ Floral diagram, _94_, 95, _96_ Flower, 83, _84_, _85_, +86+, _87_, 89, 90, _93_, _94_, 95, _96_, 97, 99, 105, 106, 112 Flowering glume--the outer palea Flowering stem, 83, 84 Flying Bent--_Molinia cærulea_ Folded leaves, 15, _16_, 20, 24, 25, 63, _69_, 70, 74 Foreign grasses, 30 Forestry, 3 Forest species, 27, 28, 33 Form of lamina, 19, 20 Foxtail grass--_Alopecurus_ Foxtail type of inflorescence, _9_, 88, 100 Fructification--fruiting, 120 Fruit, 119, 123, 125, _126_, _129_, +134+, +135+-+174+ Fruit-coats, 121, 122 Functions of awns, 95, 125, _126_, 127 Functions of ears, 19 Functions of leaves, 2 Functions of ligule, 18, 19 Functions of lodicules, 96 Functions of spear, 132 Furrows, 23, 78 _Gastridium_--Nit-grass, 90, 91, 101, 103, 105; _G. lendigerum_, 31 Germination, 123, +131+-+133+ Germination of pollen-grain, _120_, 121 Giant Fescue--_Festuca gigantea_ Girders--supporting bands of sclerenchyma running in the principal ribs and ridges, _63_, _64_, 65, _66_, _67_, +68+, _69_, 70, 71, 74-80 Glabrous--devoid of hairs, 18, 19, 22, 26, 45, 48, 80, 168 Glaucous--pale sea-green, usually due to a waxy bloom, 22 Glume, 85, 86, _87_, +91+, +92+, 93, +94+, 95, 99-118, 124, 125, 127, 130, 134, 135, 136, 151, _152_, _153_, _154_, _155_, 156 _Glyceria_--Sweet-grass, 6, 14, 20, 21, 37, 40, 54, 67, 90, 91, 92, 136, 137, 138, 146, 148; _G. aquatica_, 6, 11, 16, 17, 25, 26, 28, +39+ 54, 69, +73+, 103, 111, 112, +113+, 142, +145+; _G. distans_--_Poa distans_; _G. fluitans_, 6, 11, 16, 17, 25, 28, 32, +39+, 40, 54, 64, 66, 69, +73+, +111+, 113, _128_, +145+; _G. maritima_--_Poa maritima_; _G. procumbens_--_Poa procumbens_; _G. rigida_--_Poa rigida_ Grain, 86, 95, 121, _122_, 127, 135 Graminaceæ, characters, 3, 36, 37 Gramineæ, _see_ Graminaceæ Grass, origin of the word, 3 Grass carpets, 2, 37 Grasses, identification of, 3, 4 Grazing, 27 Grey Hair-grass--_Aira canescens_ Grooved leaf, _69_, 70, _71_, 79 Grooved sheath, 18 _Gynerium_, 89 Habit, 13, 34 Habitats, 27-31 Hair-grass--_Aira_ Hairs, _18_, 19, 21, 24, 26, 62, 64, 66, 67, 91, 125, 130, 131, 138, 139, 144 Hair-tufts, 59, 123, 125, _129_, _158_ Hairy grasses, _18_, 19, 21, 22, _23_, +26+, 57, 76, 81 Hairy Brome--_Bromus asper_ Hairy “seeds,” 168 Half-shade species, 34 Halophytes, 36 Hard Fescue--_Festuca duriuscula_ Hard-grass--_Lepturus_ Hard leaves, 21, 47 Hard Meadow-grass--_Poa rigida_ Hardy Bamboos, 38 Hare’s-tail--_Lagurus_ Harsh leaves, 21 Haulm, 83 Havers--_Avena fatua_ Hay, 27, 37 Heath False-Brome--_Brachypodium pinnatum_ Heath-grass--_Triodia decumbens_ Heath-grasses, 20, +29+, 36 Height, 6 _Heleochloa_, 123 Herbaceous--of the ordinary soft texture of herbs, 6, 21, 91 _Heterodera_, 10 Heterophylly, 71 _Heteropogon contortus_, 127 _Hierochloe_--Holy-grass, 20, 27, 66, 73, 91, 92, 105, 155; _H. borealis_, 30, 65 Hill-pastures, 29 Hispid--covered with stiff and rather long hairs, 58 Histology, 62-71, 122 _Holcus_--Soft grass, 8, 22, 26, 27, 56, 89, 90, 91, 93, +106+, 119, 125, 148, 151, _152_, _153_, 155; _H. lanatus_, 7, 11, 13, 14, 17, _23_, 26, 28, 30, 32, 34, +59+, 65, 69, +81+, +106+, 143, 151, +152+; _H. mollis_, 11, 28, 30, 33, 59, +106+, +153+ Holy-grass--_Hierochloe_ Hooded leaf-apex, 21 Hook-hairs, 65 _Hordeum_--Barley, 10, 20, 22, 26, 44, 59, 88, 89, 90, 92, +99+, 100, 108, 127, 134, 163; _H. jubatum_, 125; _H. maritimum_, 8, 10, 29, 33, 59, +100+, +163+; _H. murinum_, 8, 10, 14, 21, 30, 50, +59+, +76+, +100+, 125, 162, +163+; _H. pratense_, 7, 11, 14, 21, 22, 28, +58+, +100+, +163+; _H. sylvaticum_, 7, 11, 14, 28, 34, 44, +58+, 59, +100+, 105, +162+ Humus species, 33, 35 Hybrids, 120 Hydrophytes--plants requiring much water, and therefore aquatic or semi-aquatic, 37 Hygrophilous species--hydrophytes, 70 Imperfect--rudimentary or staminate, 105 Inconspicuously awned grasses, 93 Indicator-plants, 31, 32, 34 Inflorescence, _5_, _9_, _12_, _15_, 83, +86+-+91+, 97, 99, 102, 103, 105, 106, +109+-+118+, 119 Infolding of leaves, 20, 23, 25, 62, +63+, 64 Inrolling of leaves, 20, 23, 25, 46, 62, +63+, 64, _65_, _66_, _67_, _69_, 75, 78, 79, 80 Intercellular spaces, 37 Internode, 8, 17 Intra-vaginal shoots, 12, 13 Introduced grasses, 30 Involute--rolled inwards, 20, 47 Irritability of seedlings, 132 Italian Rye-grass--_Lolium italicum_ Keel, 18, _23_, 26, _63_, 68, 69, 91, 113, 127, 140, 144, 146, 147, 148, 149, 151 Keeled grasses, 26, 74 _Knappia_--_Mibora_ Kneed awns, _129_, 130, 151, 153, _154_, _158_ Kneed stem, _9_ Knot-grass--_Polygonum_ _Kœleria_, 11, 14, 19, 20, 25, 26, 90, 91, 92, 101, 103, 110, 141, 146, _149_; _K. cristata_, 8, 29, 32, 66, +81+, +109+, 148, +149+ Lacunæ--air-spaces, 70, 73 _Lagurus_--Hare’s-tail, 76, 88, 90, 92, 100, 101, 109; _L. ovatus_, 31 Lamina--the blade of the leaf, 63-71, 95 Lanceolate--narrow and tapering at both ends, 163 Lanceolate-acuminate--lanceolate, but the upper end drawn out to a long point, 163 Large grasses, 6 Lawns, 10, 37 Lax--loose, the spikelets on slender branches some distance apart, 110, 117 Layed shoots, 15 Leaf, +17+-+27+, 39-61, 95, 133 Leaf anatomy, 62-71, 72-82 Leaf-apex, +21+ Leaf-base, 10, 22, 40 Leaf-blade--Lamina Leaf characters, 4, +20+-+27+ Leaf-margin, +22+, 44, 66 Leaf-section, _16_, 20, +62+-+72+ Leaf-stalk--Petiole Leaf-surface, +22+, 65, 66, 67 Least Quaking-grass--_Briza minor_ Leathery leaves, 21 _Leersia_--Cut-grass, 67, 70, 77, 90, 91, 92, 105, 120; _L. oryzoides_, 30, 66, 137 Leguminosæ, 3 _Lepturus_, 87, 90, 99; _L. filiformis_--_L. incurvatus_; _L. incurvatus_, 31 Ligule, _18_, _19_, 45, 46, 51, 95, 113, 133 Limestone species, 32 Linear--at least five times as long as broad, with parallel straight sides, 19 Linear-acuminate--linear, but tapering to a long point at the apex, 19 Linear-acute--linear, but pointed at the apex, 39 Linear-lanceolate--linear, but tapering at both ends, 19, 20, 163, 168 Linear-oblong--oblong, but drawn out so that the sides are parallel for some distance, 16 Local grasses, 30, 31 Lodicules, 86, _87_, 95, _96_, 97 _Lolium_--Rye-grass, 13, 14, 18, 22, 25, 49, 50, 53, 57, 59, 82, 88, 90, 91, +107+, 108, 109, 144, 151, 167; _L. italicum_, 7, 11, 28, 31, +49+; _L. perenne_, 8, 11, 16, _19_, 20, 28, 30, 32, +49+, +81+, 82, 93, +107+, 128, 131, +142+, 143, 144, 150, 168; _L. temulentum_, 8, 10, 30, +49+, 50, 82, 92, +107+, _129_, 130, 142, 150, 167, +168+ Loose Panic-grass--_Panicum Crus-galli_ _Lygeum_, 36 Lyme-grass--_Elymus_ Maize, 1, 89, 120 Male flowers, 89, 90, 119 Manna-croup--_Glyceria fluitans_ Many-flowered spikelets, 90 Margin of leaf, 21, +22+, 66 Marginal asperities, 22 Maritime grasses, 29 Marram--_Psamma_ Marsh Bent--_Agrostis alba_ Marsh Foxtail--_Alopecurus geniculatus_ Marsh grasses, 28, 29 Mat-grass--_Psamma arenaria_ Maydeæ, 122 Meadows, 1 Meadow Barley--_Hordeum pratense_ Meadow Fescue--_Festuca elatior_--_Festuca pratensis_ Meadow Foxtail--_Alopecurus pratensis_ Meadow-grass--_Poa pratensis_, 83 Meadow grasses, +27+, +28+, 37, 113 Meadow Soft-grass--_Holcus lanatus_ Mechanical tissues--tissues composed of hard-walled cells (sclerenchyma) serving for support, 62, _63_, _64_, 68 Medium grasses, 7 _Melica_--Melick, 11, 14, 16, 19, 20, 23, 25, 26, 34, 63, 90, 91, 92, 110, +136+, 137, 142; _M. ciliata_, 32; _M. nutans_, 7, 17, 33, +41+, 78, 104, 105, +137+; _M. uniflora_, 7, 17, 28, 33, +40+, 41, 78, 104, +105+, 137 _Melocanna_, 123 Membranous ligule, 19 Mesophytes--plants adapted to ordinary conditions of moisture, 37 _Mibora_, 68, 87, 89; _M. verna_, 31, +74+, +99+ Micropyle, _121_ Microscopic characters, 62, 122 Mid-rib, 15, 20, 21, 25, _63_, 67, 68, 74 _Milium_--Millet-grass, 6, 11, 14, 20, 22, 27, 34, 89, 91, 92, 137; _M. effusum_, 6, 28, 33, +103+, +136+ Millet--_Panicum_, 135 Millet-grass--_Milium_ Millet-seed type, 127, +135+ Moist soils, 26, 32 _Molinia_, 8, 14, 19, 20, 40, 60, 77, 90, 91, 92, 146, 148, 151, 171; _M. cærulea_, 7, 26, 29, 32, 33, 36, 37, 40, +59+, +110+, +148+, _149_ Monocotyledons, 97, 134 Monœcious--male and female flowers on the same plant, 119 Moor-grass--_Sesleria_ Moor-grasses, 8, 20, +29+, 37 Moor Mat-grass--_Nardus stricta_, 83 Morphology of flower, 95, 96, 97 Morphology of spikelet, 94 Motor-cells, 25, 41, 62, +63+, 64, _65_, _66_, _67_, _69_, 70, _71_, 73, 74, 75, 76, 77, 78, 79, 80 Mountain Melick--_Melica nutans_ Movements of awns, 125, _126_, 127 Movements of seedlings, 132 Mucronate--with a short point suddenly springing from a rounded apex, 22, 138, 139, 146, 149, _150_ _Myosotis_, 3 Naked fruits, 136 _Nardus_, 8, _9_, 11, 14, 20, 21, 64, 65, 66, 67, 70, 80, 83, 87, 88, 89, 90, 91, 93, 94, 130, 146, 171; _N. stricta_, 8, _9_, 29, 33, 36, +46+, 64, _69_, 70, +99+, 171, _173_, +174+ Narrow-leafed Oat--_Avena pratensis_ Narrow Small-reed--_Calamagrostis stricta_ Naviculate--Boat-shaped, but pointed at both ends, 16 Nematode worms, 10 Nerves--minute veins on paleæ, 113, 115, _128_, _140_, 144, 168 Nodes, 6, 8, 12, 14, 15 Nodules, 10 Northern Holy-grass--_Hierochloe borealis_ Nucellus--the body of the ovule or young seed, _122_ Nuclei, 121 Numbers of grasses, 2 Oat--_Avena_, 85, 89, +133+ Oat-type of “seed,” 156 Obsolete--so much reduced as to be practically absent, 19, 45, 48, 115, 116 Obtuse--rounded off and blunt at the apex, 19, 91 Odours, 27 Offsets, 12 _Olyra_, 6 One-flowered spikelets, 89 One-glumed Fescue--_Festuca uniglumis_ Open panicle--one where the primary branches stand off at right angles from the rachis, 112 Orange spiked Foxtail--_Alopecurus fulvus_ Orchids, 2 Ovary, 86, _87_, 89, 95, _96_, 97, 119, 121 Ovate-acute--egg-shaped in outline, but the free narrow end pointed, 61 Ovate-lanceolate--ovate, but tapering above, 168 Pale--Palea, 86, 89 Palea, _84_, _85_, 86, _87_, +92+, _93_, 95, _96_, 97, 99-118, 119, 120, _124_, 125, 127, _128_, _129_, 130, 131, 134, +135+-+174+ Pampas-grass, 1 Panic-grass--_Panicum_ Panicle, _5_, _12_, 87, 88, 90, 91, 103, 105, 109-118 _Panicum_, 4, 19, 67, 69, 72, 87, 90, 92, 101, 105, 109, 124, 135, 136, 137, 142; _P. Crus-galli_, 137; _P. glaucum_, 30; _P. plicatum_, 21; _P. sanguinale_, 30; _P. verticillatum_, 30 Papillæ--protruding cells not long enough to be termed hairs, 64, 67 Pappus, 125 Parallel venation, 21, 22 Parenchyma--ordinary soft cellular tissue of herbaceous parts, 64, 65 Partial inflorescence, 86 Pasture, 1, 10 Pasture-grasses, +27+, +28+, 37 Perennial Beard-grass--_Polypogon littoralis_ Perennial grasses, 10, 11, 40, 43, 58, 114 Perennial Oat--_Avena pratensis_ Perennial Oat-grass--_Avena pratensis_ Perfect flowers, 89, 90, 99, 100, 105, 106 Perianth--the floral coverings, 96 Pericarp--the coats of the true fruit, _121_, _122_ Petiole, 5, 17 _Phalaris_--Canary grass, 88, 101, 109, 136; _P. arundinacea_--_Digraphis arundinacea_; _P. canariensis_, 31, 139 _Phleum_, 66, 88, 89, 90, 91, 93, +102+, 109, 110, 136, 137, 142; _P. alpinum_, 30, 102; _P. arenarium_, 7, 10, 29, 37, +55+, +102+, 136; _P. asperum_, 31, 55, 102, 136; _P. Bœhmeri_, 8, 31, 55, 102, 136; _P. nodosum_--var. of _P. pratense_; _P. phalaroides_--_P. Bœhmeri_; _P. pratense_, 7, 8, 11, 13, 25, 28, 32, +55+, 70, +76+, +102+, _128_, +135+ Phloem, 67 _Phragmites communis_--_Arundo Phragmites_ Physiognomy, 36, 37 Piercing of soil, 132 Pilose--with scattered, rather long soft hairs, 59 Plaited vernation, 21 _Plantago_, 3 Plicate--plaited Plume-like inflorescence, 91, 103 Plumule, _121_, 123, 132, 133 _Poa_, 2, 15, 20, 21, 23, 25, 26, 47, 54, 61, 74, 83, 84, 88, 89, 90, 91, 92, 103, 104, 109, 110, +113+, 114, 115, 116, 118, 127, 131, 140, 141, 144, 146, 151, 162; _P. alpina_, 8, 11, 13, 14, 16, 17, 31, +44+, 54, 63, 114, 134, +146+; _P. annua_, 8, 10, 14, 16, 30, 34, 42, +53+, 54, _63_, 68, 74, 75, +114+, _127_, 141, +146+; _P. aquatica_--_Glyceria aquatica_; _P. bulbosa_, 8, 11, 14, 29, +54+, 69, 111, 114, 146; _P. compressa_, 8, 11, 14, 15, 16, 30, 32, 42, +53+, 54, 63, 69, 74, 111, +114+, 139, +140+; _P. distans_, 29, 30, 114, 146; _P. fertilis_--_P. serotina_, 45; _P. fluitans_--_Glyceria fluitans_; _P. laxa_, 31, 134; _P. loliacea_, 31, 108, 114, 146; _P. maritima_, 8, 11, 14, 16, 20, 22, 26, 29, +47+, 54, +111+, 114, 146; _P. nemoralis_, 7, 11, 14, 15, 28, 34, 45, +54+, 63, 74, 75, 113, +114+, 139, _140_, +141+, 161; _P. pratensis_, 7, 11, 13, 14, 16, 17, 27, 32, 33, 41, 42, +44+, 45, 54, 55, 67, 75, 113, +114+, 139, +140+, 141; _P. procumbens_, 31, 111, 114; _P. rigida_, 10, 14, 30, +111+, 114, 146; _P. stricta_--var.of _P. alpina_, 134; _P. trivialis_, 7, 11, 13, 14, 16, 17, _18_, 27, 32, +42+, 44, 45, 54, +74+, 90, 112, +113+, 139, _140_, +141+, 146, 148 Pollen, _93_, 94, 119 Pollen-grain, _120_, +121+ Pollen-tube, _120_, +121+ Pollination, _93_, 119, +120+, +121+ _Polygonum_, 3 _Polypogon_--Beard-grass, 69, 90, 91, 92, 100, 101, 109; _P. littoralis_, 31; _P. monspeliensis_, 31 Ponds, grasses of, 28, 29 Popular names, 6 Potassium salts, 32 Prairies, 1, 36, 38 Prickle-hairs, 66 Primary root, 123, 131 Procumbent Meadow-grass--_Poa procumbens_ Protandrous--when the pollen is mature and shed before the stigma of the same flower is ready for pollination, 119 Proterogynous--when the stigma is receptive before the pollen of the same flower is mature, 119 _Psamma_, 4, 11, 13, 14, 21, 25, 36, 48, 79, 81, 89, 90, 92, 95, 138; _P. arenaria_, 7, 29, 33, 35, 36, +48+, 70, +79+, +102+, 138, +139+ Pubescence--hairiness, 26 Pungent--spine-like, 22 Purple-flowered Small-reed--_Calamagrostis lanceolata_ Purple-stalked Cat’s-tail--_Phleum Bœhmeri_ Purple-veined sheaths, 18 Quadrangular shoot-section, 16, 40 Quake-grass--_Briza_ Quaking-grass--_Briza media_ Racemous--like a raceme, 105 Rachilla, 85, _123_, _124_, _128_, _129_, 131, _137_, 138, 142, _143_, 144, _149_, _150_, _164_, _167_, _169_, _170_, _172_ Rachis, _9_, 85, 88, 106, 107 Radicle, _121_, 123 Rare grasses, 6, +30+, +31+, 89, 90, 91, 92 Rat’s-tail Fescue--_Festuca Myurus_ Red-sheathed grasses, 18, 49, 59 Reed, 2 Reed Canary grass--_Digraphis arundinacea_ Reed Fescue--_Festuca sylvatica_ Reed-grass, 1, 6 Reed Meadow-grass--_Glyceria aquatica_ Reed Sweet-grass--_Glyceria aquatica_ Reflexed leaves, _16_ Reflexed Meadow-grass--_Poa distans_ Rhizomes, 10, 11, 35, 36, 37 Rhomboidal shoot-section, 16, 42 Rib-grass--_Plantago_ Ribbon-grass--_Digraphis arundinacea_ Ribs--the more opaque veins due to the larger vascular-bundles, 22, 25, 62, 91, _127_ Rice, 1 Ridgeless grasses, 25 Ridges, _18_, 21, 22, +23+, _24_, +25+, 26, 47, 51, 53, 54, _65_, _66_, _67_, 68, _69_, _71_, 73, 77, 78, 79, 80, 91 River-banks, 28, 29 Road-sides, 29 Rolled leaves, 15, _16_, 20, 24, 25, 63 Rolling of leaves, 24, 25, 36 Root-cap, _121_ Roots, 8, 12, 35, _121_, 123, 131, 132, 133 Rough Cock’s-foot--_Dactylis glomerata_ Rough Meadow-grass--_Poa trivialis_ Rough Phleum--_Phleum asperum_ Rough-stalked Meadow-grass--_Poa trivialis_ Round shoots, 15, _16_, 42, 50, 57 Ruderal grasses, 29, 32, 34, 35 Rudimentary flowers, 89, 90, 105 Runners, 12, 13, 14 Rushes, 4, 33 Rushy Wheat-grass--_Agropyrum junceum_ Rye--_Secale_, 120, 132, +133+ Rye Brome--_Bromus secalinus_ Rye-grass--_Lolium perenne_ Salt species, 33 Sand-binders, 13, 35, 36, 48, 102, 107, 108 Sand Cat’s-tail--_Phleum arenarium_ Sand dunes, 35, 36 Sand species, 29, 32, 36 Sandy situations, 8, 29, 33 Savannahs, 1, 38 Scaberulous--slightly rough to the touch, 22, 45, 164 Scabrid--rough to the touch, 22, 47, 54 Scarious--as if scorched by fire, 92, 145 Scents, 27 Sclerenchyma--mechanical tissue, 62, _65_, _66_, _67_, +68+, _69_, 70, _71_, 74, 75, 76, 79, 80 _Sclerochloa_--_Poa_ _Sclerochloa maritima_--_Poa maritima_; _S. procumbens_--_Poa procumbens_; _S. rigida_--_Poa rigida_ Scorpion-grass--_Myosotis_ Scutellum, _121_, 123 Sea Barley--_Hordeum maritimum_ Sea Cat’s-tail--_Phleum arenarium_ Sea-grass--_Zostera_ Sea Hard-grass--_Lepturus incurvatus_ Sea Lyme-grass--_Elymus arenarius_ Sea Mat-grass--_Psamma arenaria_ Sea Mat-weed--_Psamma arenaria_ Sea Meadow-grass--_Poa maritima_ Sea Poa--_Poa maritima_ Sea Reed--_Psamma arenaria_ Sea-side grasses, 27, 29 Secondary roots, _121_, 123, 131, 133 Secund--turned to one side, _9_, 89, 108, 109, 114 Sedges, 3, 4, 33, 35, 121 Seed--strictly the contents of the caryopsis (fruit), but in practice the fruit and its adherent paleæ etc. (chaff) are termed “seed,” 119, 120, 121, 123, +124+, 125, _127_, 128, 129, 130, _131_, +134+, +135+-+174+ Seed-coats, 121, _122_ Seedlings, 132, +133+ Semi-aquatic species, 28, 29 Separation of fruits, _124_ Serrulæ--minute tooth-like asperities, 22, 91, _173_ _Sesleria_--Moor-grass, 22, 25, 63, 64, 68, 90, 91, 93, 101; _S. cærulea_, 17, +42+, 67, +108+, 149, +151+ Sessile--sitting directly on an axis without an intervening stalk, 87, 99, 107 Setaceous--bristle-like, _16_, 19, 20, 21, _24_, 45, 111, 113 _Setaria_--_Panicum_ Sexual organs, 134 Shade action of grasses, 35 Shade-grasses, 20, +28+, 33, 34, 70 Shapes of caryopsis, 127 Shapes of leaves, 4, 19, 20 Shapes of shoot, 16 Sharp-edged shoots, 16 Sheath, 5, 8, 12, 15, _16_, 17, _18_, _19_, 20, 22, 51, 95, 133 Sheep’s Fescue--_Festuca ovina_ Shelving sheath-margin, 22 Shoot, 10, 12, 15, 16, 123 _Sieglingia decumbens_--_Triodia decumbens_ Siliceous--impregnated with flint--silex, 64, 65, 66 Silky Bent-grass--_Agrostis Spicaventi_ Silvery Hair-grass--_Aira caryophyllea_ Single-husked Fescue--_Festuca uniglumis_ Slender Foxtail--_Alopecurus agrestis_ Small grasses, 7 Small Reed--_Calamagrostis_ Smooth Brome--_Bromus racemosus_ Sociable plants, 36 Sod, 37 Sodium chloride, 33 Soft Brome--_Bromus mollis_ Soft-grass--_Holcus_ Soft Holcus--_Holcus mollis_ Soil formation, 36 Soil protection, 36 Solid leaves, 46 Solid stems, 4 Sour soils, 33 _Spartina_--Cord-grass, 69, 87, 90, 99, 105; _S. stricta_, 27, 31, 78 Spear, 123, 132 Spikate inflorescence, 99, 106 Spike, _9_, 87, 88, 90, 99, 100, 101, 102, 106, 108 Spiked Fescue--_Festuca loliacea_ Spikelet, 9, _84_, _85_, +86+, _87_, 88, +89+, +90+, _93_, _94_, 95, 97, 99-118, 119, 120, 123, _124_ Spike-like panicle, _9_, 88, 90, 102 Spinescent leaf, 22 _Spinifex_, 125 Split sheath, 5, 17, _18_, _19_ Split-sheathed grasses, 17, _18_, _19_, 45, 50 _Sporobolus_, 123, 134 Squirrel-tail grass--_Hordeum maritimum_ Stamen, 86, _87_, 89, _93_, 94, 95, _96_, 97, 102, 103, 119 Staminate--a flower with stamens and no ovary, 100, 105, 106 Starch, 120, 121, 122 Stem, 4, 6, 8 Steppes, 1, 36, 38 Stigma--stigmatic plumes, 86, _87_, _93_, 94, 96, 97, +119+, _120_, 121 _Stipa_, 36, 96, _126_; _S. capillata_, 125; _S. pennata_, 32, 125; _S. spartea_, 125 Stolon, 10, 12, 35, 114 Stoloniferous grasses, 8, 13, 14, _15_ Stomata, 25, 36, 62, 64, 65, 67, 70, 73, 77, 80, 95 Strand-plants, 36 Stringy roots, 8 Striped grass--_Digraphis arundinacea_ Struggle for existence, 2, 37, 38 Style, 94, 97, 99 Sub-acute--hardly pointed, 142 Sub-sessile--very shortly stalked, so as to be all but sessile, 99, 106 Sub-terminal awn, 95, 115, _129_, 130, _150_, 151, _152_, 162, 163-168, _169_ Subulate--awl-shaped: stouter than setaceous, 19, 20, 21, 70, _71_, 79 Sugar, 120, 121, 122 Sugar-cane, 1 Sun-plants, 36 Sweet-tasting grasses, 39 Sweet Vernal grass--_Anthoxanthum odoratum_ Sympodium, 11 Tall Brome--_Bromus giganteus_ Tall Fescue--_Festuca elatior_ Tapering leaves, 21 Tastes, 27 Temperate species, 2 Terete--cylindrical and gradually tapering, 6, 54, 163, 171 Terminal awn, 92, 111, 115, 116, _126_, +130+, 162, 168-174, _173_ Texture of leaf, +21+ Three-flowered spikelets, 90 Timothy--_Phleum pratense_ Tomentose--softly hairy, 59 Transpiration, 20 Transverse sections of leaves, _16_, _23_, _24_, _63_, _64_ Transverse section of shoot, 15, 16 _Triodia_--Heath-grass, 11, 14, 19, 25, 26, 90, 91, 103, 139; _T. decumbens_, 8, 29, 34, +110+, _123_ _Trisetum flavescens_--_Avena flavescens_ _Triticum_--Wheat; _T. acutum_--_T. laxum_; _T. junceum_--_Agropyrum junceum_; _T. laxum_--_Agropyrum laxum_; _T. pungens_--_T. laxum;_ _T. repens_--_Agropyrum repens_ Tropical species, 1, 2 Truncate, 92, 142 Tuber, 8 Tufted grasses, 13, 14 Tufted Hair-grass--_Aira cæspitosa_ Tufted inflorescences, 90, 99, 102, 103, 109 Tufts, _5_, _9_, 12, 13, 37 Tumble-weeds, 125 Turgescence--the distension of cells with water which they have absorbed, 63 Tussocks, 13 Twisted awns, 116, 125, _126_, _129_, 130, 151, 154, _158_ Twisting of seedling leaves, 133 Twitch--certain persistent weeds belonging to the genera _Agropyrum_, _Agrostis_, _Holcus_, etc.: _see_ Couch-grass, 52, 57, 59 Two-flowered spikelets, 90 +U+-shaped leaf-sections, 20 _Uniola_, 97 Upright Brome--_Bromus erectus_. Also _B. madritensis_ Uses of grasses, 1, 2 +V+-shaped leaf-sections, 20, 53, 73 Vagabond grasses, 29, 32, 34 Variability, 26 Vascular bundles, 21, 22, 62, _63_, _64_, _65_, _66_, _67_, +68+, _69_, 70, _71_, 75, 76, 78, 80, 81 Vascular-bundle sheath, 68, 95, _122_ Vegetative organs, 4 Veins, 18, 21, 22, 68, 76, 91 Venation, +21+, 62, +67+, 68 Vermin, 35 Vernal grass--_Anthoxanthum_, 83 Vernation--folding of the leaves in bud, 21 Versatile--hung loosely so as to turn freely, 94 Vessels, 67 Violet-brown sheath, 18 Viviparous grasses, 112, 114, 134 _Vulpia Myurus_--_Festuca Myurus_; _V. uniglumis_--_Festuca uniglumis_ Wall Barley--_Hordeum murinum_ Wall Fescue--_Festuca Myurus_ Walls, grasses of, 29 Waste-places, 29 Water-storing tissues, 36, 70 Water Whorl-grass--_Catabrosa aquatica_ Wavy Hair-grass--_Aira flexuosa_ Wavy Meadow-grass--_Poa laxa_ Wax, 36, 70 Web--minute tufted soft hairs at the base of the caryopsis, 113, 114, _127_, 131, 138, 139, _140_, 141 Weeds, 27, 28, 29, 35 Wheat--_Triticum_, 1, 120, 127, 132, +133+ Wheat-grass--_Agropyrum_ Whorl-grass--_Catabrosa_ Wild Oat--_Avena fatua_, 117 Wind-borne seeds, 125, _126_ Wings, 125, 142 Wood Barley--_Hordeum sylvaticum_ Wood False-Brome--_Brachypodium sylvaticum_ Wood Meadow-grass--_Poa nemoralis_ Wood Melick--_Melica uniflora_ Wood Poa--_Poa nemoralis_ Wood-species, +28+, 33 Woolly Holcus--_Holcus lanatus_ Xenia--cases where the direct influence of the pollen is evident on the seed resulting from its action, 120 Xerophilous--of the nature of a xerophyte, 70 Xerophytes--plants adapted to dry situations, 24, 25, 36, 37, 38, 68, 70 Xylem, 67 Yellow Oat-grass--_Avena flavescens_ Yellow-sheathed grasses, 18 Yorkshire Fog--_Holcus lanatus_, 152 _Zostera_, 3 CAMBRIDGE: PRINTED BY JOHN CLAY, M.A. AT THE UNIVERSITY PRESS. CAMBRIDGE BIOLOGICAL SERIES +The Elements of Botany.+ By FRANCIS DARWIN, Sc.D., M.B., F.R.S., Fellow of Christ’s College. _Second edition._ Crown 8vo. With 94 illustrations. 4_s._ 6_d._ _Journal of Education._ A noteworthy addition to our botanical literature. +Practical Physiology of Plants.+ By FRANCIS DARWIN, Sc.D., F.R.S., and E. HAMILTON ACTON, M.A. _Third edition._ Crown 8vo. With 45 illustrations. 4_s._ 6_d._ _Nature._ The authors are much to be congratulated on their work, which fills a serious gap in the botanical literature of this country. +Morphology and Anthropology.+ By W. L. H. DUCKWORTH, M.A., M.D., Fellow and Lecturer of Jesus College, University Lecturer in Physical Anthropology. Demy 8vo. With 333 illustrations. 15_s. net_. _Athenæum._ Mr Duckworth has managed to produce in his “Morphology and Anthropology” just such a text-book as students have long been asking for.... It is no easy task to have undertaken such a work and the author is to be congratulated on the success which has attended his efforts. The volume can be confidently recommended to all whose studies lead them in this direction. +Lectures on the History of Physiology+ during the Sixteenth, Seventeenth and Eighteenth Centuries. By Sir M. FOSTER, K.C.B., M.D., D.C.L. Demy 8vo. With a frontispiece. 9_s._ _Nature._ There is no more fascinating chapter in the history of science than that which deals with physiology, but a concise and at the same time compendious account of the early history of the subject has never before been presented to the English reader. Physiologists therefore owe a debt of gratitude to Sir Michael Foster for supplying a want which was widely felt.... No higher praise can be given to the book than to say that it is worthy of the reputation of its author. +The Soluble Ferments and Fermentation.+ By J. REYNOLDS GREEN, Sc.D., F.R.S., Professor of Botany to the Pharmaceutical Society of Great Britain. _Second edition._ Demy 8vo. 12_s._ _Nature._ It is not necessary to recommend the perusal of the book to all interested in the subject since it is indispensable to them, and we will merely conclude by congratulating the Cambridge University Press on having added to their admirable series of Natural Science Manuals an eminently successful work on so important and difficult a theme, and the author on having written a treatise cleverly conceived, industriously and ably worked out, and on the whole, well written. +Conditions of Life in the Sea.+ A short account of Quantitative Marine Biological Research. By JAMES JOHNSTONE, Fisheries Laboratory, University of Liverpool. Demy 8vo. With a chart and 31 illustrations. 9_s. net_. +The Natural History of some Common Animals.+ By OSWALD H. LATTER, M.A., Senior Science Master at Charterhouse. Crown 8vo. With 54 illustrations. 5_s. net_. _Nature._ An excellent book, written by a man who is equally in his element whether he writes as an outdoor naturalist or as a laboratory student. This combination is by no means a common one, and it is just the combination that is wanted for a book of this kind.... Altogether the book is an admirable one. _Athenæum._ A book that may be judiciously placed in the hands of any boy who evinces a reasonable interest in the animal life around him. +The Classification of Flowering Plants.+ By ALFRED BARTON RENDLE, M.A. (Cantab.), D.Sc. (Lond.), F.L.S., Keeper of the Department of Botany, British Museum. Vol. I. Gymnosperms and Monocotyledons. Demy 8vo. With 187 illustrations. 10_s._ 6_d._ net. _Gardener’s Chronicle._ Numerous illustrations and an excellent index add to the value of the work. We heartily congratulate the author on the partial accomplishment of a difficult and laborious task. The part before us does but whet our appetite for what is to follow. _Athenæum._ The first instalment of a text book which will well represent the state of our knowledge in the early years of the century. In the present volume the Gymnosperms and the Monocotyledons alone are dealt with; but they are treated with such excellent co-ordination of detail and such clear-headed sense of proportion, that we eagerly await the publication of the next instalment. +The Origin and Influence of the Thorough-bred Horse.+ By W. RIDGEWAY, Sc.D., F.B.A., Disney Professor of Archæology and Fellow of Gonville and Caius College. Demy 8vo. With 143 illustrations. 12_s._ 6_d. net_. _Westminster Gazette._ There has never been a more learned contribution to equine literature than Professor Ridgeway’s comprehensive and exhaustive book. _Spectator._ It would be difficult for Professor Ridgeway to write a book which did not contain at least one wholly novel thesis, and the present work is no exception to his practice. It is also an encyclopaedia of information on the history of the _Equidae_, collected from every source, from post-Pleiocene deposits to modern sporting newspapers. No detail escapes the author’s industry, and ... the result is a monument of sound learning, unique of its kind. +Manual of Practical Morbid Anatomy+, being a Handbook for the Post-mortem Room. By H. D. ROLLESTON, M.A., M.D., F.R.C.P., and A. A. KANTHACK, M.D., M.R.C.P. Crown 8vo. 6_s._ +Fossil Plants: a text-book for students of Botany and Geology.+ By A. C. SEWARD, M.A., F.R.S., Professor of Botany in the University of Cambridge. In 3 vols. Demy 8vo. Vol. I. with a frontispiece and 111 illustrations, 10_s. net_. Vol. II. with a frontispiece and 265 illustrations. 15_s. net_. [Vol. III in the Press. _Revue Scientifique._ Nous ne pouvons entrer dans le détail; mais il est évident que M. Seward, praticien distingué lui-même, est très au courant des travaux des autres, il les cite et utilise abondamment; et ceci est fait pour inspirer confiance. Au total, son œuvre est appuyée sur des bases solides, et elle restera sans doute longtemps le bréviaire, le manuel de ceux qui veulent, non pas seulement s’initier à la paléobotanique, mais retrouver les renseignements qui sont épars dans des centaines de monographies qu’on a souvent peine à se procurer. Le livre de M. Seward fait partie des _Cambridge Natural Science Manuals_, et il est digne de cette collection, qui est elle-même digne du foyer scientifique universellement réputé, où il a vu le jour. +Zoology. An Elementary Text-Book.+ By A. E. SHIPLEY, Sc.D., F.R.S., and E. W. MACBRIDE, M.A. (Cantab.), D.Sc. (London). _Second edition._ Demy 8vo. With 349 illustrations. 10_s._ 6_d. net_. _Pall Mall Gazette._ Precisely the sort of book which, if it came into a thoughtful boy’s hands, would turn him from a smatterer into a student.... One of the most instructive and attractive books that could be put into the hands of a young naturalist. +Trees+: A Handbook of Forest Botany for the Woodlands and the Laboratory. By H. MARSHALL WARD, Sc.D., F.R.S. Vol. I. Buds and Twigs. Vol. II. Leaves. Vol. III. Flowers and Inflorescences. Vol. IV. Fruits. Vol. V. Form and Habit, with an Appendix on Seedlings. Crown 8vo. With numerous illustrations. 4_s._ 6_d. net each_. Price for the set of five volumes, 20_s. net_. _Nature._ The clear and simple way in which the author treats the subject is sure to inspire many with interest and enthusiasm for the study of forest botany.... The work will be found indispensable to those students who wish to make an expert study of forest botany. At the same time it is expressed in language so clear and devoid of technicalities that the amateur who wishes to know something about our trees and shrubs will find this one of the most useful guides to which he can turn.... The work is a many sided one, acting not only as a guide to the naturalist in the field, but also as a laboratory handbook, where the use of the lens and microscope may be employed to amplify the study of objects already observed in their natural habitats. Botanists generally, and especially forest botanists will welcome the appearance of this book as supplying a decided want, and filling a distinct gap in our literature of forest botany. +Grasses+: a Handbook for use in the Field and Laboratory. By H. MARSHALL WARD, Sc.D., F.R.S. Crown 8vo. With 81 figures. 6_s._ _Field._ The work is essentially suited to the requirements of those desirous of studying the grasses commonly grown in this country, and it can fairly be said that it furnishes an amount of information seldom obtained in more pretentious volumes. P. T. O. +A Treatise on the British Freshwater Algæ.+ By G. S. WEST, M.A., A.R.C.S., F.L.S., Lecturer in Botany in the University of Birmingham. Demy 8vo. With a frontispiece and 166 illustrations. 10_s._ 6_d._ _net_. _Nature._ Its aim is stated as “to give the student a concise account of the structure, habits and life-histories of Freshwater Algæ, and also to enable him to place within the prescribed limits of a genus any Algæ he may find in the freshwater of the British Islands.” To do this within the limits of an octavo volume of less than 400 pages, in which are numerous illustrations, is a task possible of accomplishment only by one very familiar with the subject and skilled in concise expression; but that it has been successfully done will, we think, be the verdict after testing the book thoroughly.... Prof. West’s treatment of his subject is instructive and stimulating. +A Manual and Dictionary of the Flowering Plants and Ferns.+ By J. C. WILLIS, M.A., Sc.D., Director of the Royal Botanic Gardens, Ceylon. _Third edition._ Crown 8vo. 10_s._ 6_d._ _Field._ Taking this handy volume and a local flora, the traveller or student may do an enormous amount of practical field work without any other botanical literature whatever.... The result is a work that ought to be included in every library of botany and horticulture or agriculture, and it is certainly one that the nomadic botanist cannot afford to leave at home.... We have used the original edition of this work since its publication, and have found it to be one of the most useful and comprehensive works on plants ever produced. _Athenæum._ The whole is well abreast of modern research, and a thoroughly business-like volume, lucid though compact. +Agriculture in the Tropics.+ An elementary Treatise. By J. C. WILLIS, M.A., Sc.D. Demy 8vo. With 25 plates. 7_s._ 6_d. net_. +Palæontology--Invertebrate.+ By HENRY WOODS, M.A., F.G.S., University Lecturer in Palæozoology. _Fourth edition._ Crown 8vo. With 151 illustrations. 6_s._ +Outlines of Vertebrate Palæontology for students of Zoology.+ By ARTHUR SMITH WOODWARD, M.A., F.R.S., Keeper of the Department of Geology in the British Museum. Demy 8vo. With 228 illustrations. 14_s._ _Athenæum._ The author is to be congratulated on having produced a work of exceptional value, dealing with a difficult subject in a thoroughly sound manner. CAMBRIDGE UNIVERSITY PRESS London: FETTER LANE, E.C. C. F. CLAY, MANAGER Edinburgh: 100, Princes Street ALSO London: H. K. Lewis, 136, Gower Street, W.C. *** END OF THE PROJECT GUTENBERG EBOOK GRASSES *** Updated editions will replace the previous one—the old editions will be renamed. 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