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There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924003505413 CAMBRIDGE BIOLOGICAL SERIES. GENERAL Epiror :—ArtTHuR E. Sarpiey, M.A. FELLOW AND TUTOR OF CHRIST'S COLLEGE, CAMBRIDGE. GRASSES. Zondon: OC. J. CLAY anv SONS, CAMBRIDGE UNIVERSITY PRESS WAREHOUSE, AVE MARIA LANE, AND H. K. LEWIS, 136, GOWER STREET, W.C. Glasgow: 50, WELLINGTON STREET. Leipsig: F. A. BROCKHAUS. few Work: THE MACMILLAN COMPANY. Bombay and Calcutta: MACMILLAN AND CO., Lrp. [All Rights reserved.] GRASSES A HANDBOOK FOR USE IN THE FIELD AND LABORATORY. BY H. MARSHALL WARD, S8c.D., F.R.S. FELLOW OF SIDNEY SUSSEX COLLEGE, HONORARY FELLOW OF CHRIST’S COLLEGE AND PROFESSOR OF BOTANY IN THE UNIVERSITY OF CAMBRIDGE. CAMBRIDGE: AT THE UNIVERSITY PRESS. 1901 Cambridge : PRINTED BY J, AND C. F. CLAY, AT THE UNIVERSITY PRESS. PREFACE. fl ae 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. 185—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 vi PREFACE 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 Teat-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, dpril, 1901. CONTENTS. CHAPTER I. PAGE THE VEGETATIVE ORGANS re ie 8 ‘ ‘ ‘ . . 1 CHAPTER II. THE VEGETATIVE ORGANS (continued) . . : 5 17 CHAPTER III. GRASSES CLASSIFIED ACCORDING TO THEIR VEGETATIVE CHARACTERS. z ‘ . 5 F ‘ F . 39 CHAPTER IV. ANATOMY AND HistoLocy z 2 : : 62 CHAPTER V. Grasses CLASSIFIED ACCORDING To THE ANATOMICAL CHARAC- TERS OF THE Luar . F ii ; ‘ . x 92 vill CONTENTS CHAPTER VI. PAGE GRASSES IN FLOWER 2 is z ‘ ‘ 83 CHAPTER VII. GRASSES GROUPED ACCORDING TO THEIR FLOWERS AND Iy- FLORESCENCES - : ‘ 2 . 99 CHAPTER VIII. THE FRUIT AND SEED. 5 fs ‘ ‘ 119 CHAPTER IX. CLASSIFICATION OF GRASSES BY THE “SEEDS” (GRAINS) . 185 BIBLIOGRAPHY . i . i 175 InprEx, GbossaRy anp List oF SYNONYMS Wi 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, &.—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. CW, 1 2 NUMBERS AND USES (CH. 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 1] ORIGIN OF THE WORD GRASS 3 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 Graminacess—also written Graminese—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 (Poly- gonum), 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 agri- culture, 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, 1—2 4 GENERAL CHARACTERISTICS [cH. 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 recog- nisable 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 deter- mination 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? (Figs. 6 and 7). Moreover the leaves are always of some elongated shape, and without 1 Some foreign grasses (Andropogon, Panicum, &c.) have solid stems, and in Psamma and some others the lower parts may be solid. 1] SHEATH 5 leaf-stalks’, but pass below into a sheath, which runs some way down the stem and is nearly always perceptibly split Fig. 1. A plant of Oat (Avena), an example of a typical grass, showing tufted habit and loose paniculate inflorescence (reduced). Figuier. 1 Leaf-stalks occur in tropical Bamboos. 6 DIMENSIONS [cH. (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’. 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 cespitosa (Tufted Hair-grass). Arrhenatherum avenaceum (False Oat). Elymus arenarius (Lyme-grass). Bromus asper (Hairy Brome). B. giganteus (Tall Brome). Festuca elatior (Meadow Fescue). fF. sylvatica (Reed Fescue). Glyceria aquatica (Reed Sweet-grass). G. fluitans (Floating Sweet-grass). Arundo Phragmites (Common Reed). 1 Tropical Bamboos branch in the upper parts and are woody. Dinochloa and Olyra are climbing grasses. MEDIUM AND SMALL GRASSES MEDIUM GRASSES. (1—3 feet.) Phleum pratense (Timothy). alvena 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). Hotcus 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 cerulea (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). 8 ROOTS AND STOLONS (cH. Aira canescens (Grey Hair-grass). A. precox (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. Myurus (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). Keleria cristata (Crested Keeleria). 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, Phlewm pratense and P. Behmeri, 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 1] TUFTED AND BULBOUS GRASSES Fig. 2. Nardus stricta. Plant showing tufted habit, and simple spikate inflores- cence, with pointed spike- lets all turned towards one side (secund) on the ra- chis (reduced). Note also the bristle-like (setaceous) leaves at length reflexed. Parnell. Fig. 3. Alopecurus geniculatus, var. bulbosus. Plant (reduced) showing habit, bulbous shoots and cylin- drical _spike-like inflorescences (Foxtail type). Notice the in- flated sheaths, and the ‘“kneed” lower parts of the ascending stems. Parnell. 10 DURATION OF LIFE [cH. soils. In old lawns, pastures, &., the roots of Poa annua and others may have nodules on them due to the presence of certain small Nematode worms, Heterodera. 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 under- ground 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 Howering 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, &e. In the following lists I have given the duration of the principal grasses, where the character is especially important. ANNUALS. Phleum arenarium. Lolium temulentum. Awa precox. Festuca Myurus. A. caryophyllea. Briza minor. Hordeum murinum. Poa rigida. HA. maritimum. P. annua. 1] ANNUALS AND PERENNIALS 11 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). Holcus lanatus. HI. mollis. Nardus. Hordeum sylvaticum. Agropyrum. Brachypodium. Bromus erectus. B. giganteus. Festuca ovina. fF. elatior. F.. sylvatica. Dactylis. Cynosurus cristatus. Briza media. Milium. Anthoxanthum. Digraphis. Phieum pratense. Alopecurus pratensis. Agrostis alba. A. canina. PERENNIALS. Psamma. Aira ccespitosa. A. flexuosa, A, canescens. Avena pratensis. A. flavescens. Arrhenatherum. Glyceria aquatica. G. fluttans. Poa maritima. P. compressa. P. pratensis. P. trivialis. P. nemoralis. P. alpina. P. bulbosa. Molinia. Melica. Triodia. Keleria. Arundo. The rhizome of a perennial grass is continued sym- podially 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 sprout- 12 BRANCHING (cH. ing shoots. The buds always arise in the axils of the lower leaf-sheaths—ie. 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!: the grasses Fig. 4. Catabrosa aquatica. Plant showing the creeping habit, rooting nodes, and paniculate inflorescence (reduced). Parnell. 1 Except, of course, in cases of virgin ground rapidly occupied by the seedlings. 1] STOLONIFEROUS GRASSES 13 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 (Zlymus, 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. Anthovanthum—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. 14 CREEPING AND TUFTED GRASSES [cH. Creeping below ground and truly stoloniferous. Agropyrum. Bromus erectus (slightly). Elymus. Festuca ovina (var. rubra, Linn.). Psamma. F. elatior (slightly). Poa pratensis. Briza (slightly). P. compressa. Glyceria. Agrostis alba (var. stolonifera). Poa maritima. Alopecurus pratensis. Melica. Brachypodium (slightly). Arundio. Tufted Grasses. Milium. Festuca sylvatica. Agrostis alba (on downs, &c.). F, Myurus. Aira cespitosa. Dactylis. A. fleauosa. Cynosurus. A. canescens. Poa rigida. A. precox. P. annua. A. caryophyllea. P. trivialis. Avena pratensis (slightly creeping). P. nemoralis. Arrhenatherum. P. alpina. Nardus (Fig. 2). P. bulbosa. Hordeum sylvaticum. Molinia. Lolium. Triodia. Bromus, Keeleria. Festuca ovina (except some varieties). Creeping above ground (with runners). Holcus lanatus. Alopecurus geniculatus. Agrostis alba (var. stolonifera). Hordeum pratense (slightly). A. 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 1] SHOOTS AND NODES 15 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, Avenu, 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 Alope- curus geniculatus, and may be so in other species if “layed” by wind, rank growth, &c. A point of considerable classi- ficatory 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. In most grasses the blades are Fig. 5. Cynodon Dactylon. : Plant (reduced) showing convolute—i.e. rolled up like the creeping and stolonifer- paper of a cigarette, one edge ous habit, and peculiar over the other—and the section eee q i spikes. Parnell. of the shoot is round (Fig. 7). In some cases, however, the leaves are conduplicate—i.e. ip 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). 16 SHOOT-SECTIONS (CH. I In these latter cases the transverse section may be elliptical—e.g. Poa pratensis and P. alpina, Briza, &c., Fig. 6. Dactylis glomerata, Fig. 7. Digraphis arundinacea, Trans- Transverse section of a verse section of a leaf-shoot (x5). leaf-shoot ( x 5). 4, con- A, sheath. 3B, convolute leaves. duplicate leaf-blade. B, Compare Fig. 14. Stebler. sheath. Stebler. or more flattened and linear-oblong—e.g. Glyceria flui- tans—with the flattened sides straight, or the section is oval but pointed more or less at each end owing to pro- jecting 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. Dactytis glomerata. Poa trivialis (Fig. 8), P. pratensis, P. alpina. Sesleria ccerulea. 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 w. 2 18 SHEATH AND LIGULE [CH. 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. Fig. 8. Poatrivialis. Fig. 9. Alopecurus Fig. 10. Avena flavescens. A, base of blade. pratensis. A, base Lettering as before B, ligule. C, of blade. B, ligule. (x2). Note the split sheath. D, culm C, sheath. Slight- sheath, the hairs and (x about 3). ly magnified. 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 11] LIGULE AND LAMINA 19 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, Keeleria and Panicum. It is represented by a tuft of hairs in Molinia, Triodia and Arundo. Fig.11. Lolium perenne. Fig.12. Festucaelatior, Fig. 13. Festuca A, base of lamina, var. pratensis. A, ovina. A, base B, ligule. C, sheath base of lamina. B, — of lamina. B, (x3). Note the low the extremely short ligular ears. C, ribs, and absence of ligule, with pointed sheath (x about hairs (glabrous). ears. C, sheath 4). Stebler. (x3). 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. lo 20 SHAPES OF LEAVES [cH. In the following native grasses the form of the lamina affords a useful character. The base tapers to the sheath below—ie. the leaf is more or less linear-lanceolate—in Molinia, Brachypodium, Melica, Milium, Keleria, 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—eg. Loliwm 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 Gilyceria the leaf-bases may show yellow or brownish triangles. 11] VENATION, TEXTURE, APEX 21 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 plated (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 can- num, Hordewm 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 22 BASE, MARGIN, SURFACE [CH. 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, Antho- canthum, 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 cespitosa, Poa maritima, Festuca elatior, Avena pratensis, Agrostis, Milium, Phleum, Briza, the minute teeth (ser- rule) 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 ur] RIDGES ON LEAVES 23 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—ie. height or thickness—and the furrows light in proportion to the thinness of the tissues there. If the contrast is very great, as in Atra cespitosa (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 striz. 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. 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, Fig. 14. Digraphis arundinacea. Transverse section of mid-rib and half the leaf (x about 6). Fig. 15. Holcus lanatus. Transverse section of leaf-blade (x 10). Fig. 16. Cynosurus cristatus. Transverse section of the leaf-blade (x20). Stebler. 24 XEROPHYTES [CH. 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. Fig. 20. Fig. 17. Transverse section of the leaf of Festuca elatior, var. pratensis (x12). Fig. 18. Ditto of the leaf of F. ovina (x15). Fig. 19. Ditto of the leaf of F. ovina, var. rubra (x35). Fig. 20. Festuca ovina, var. rubra. Transverse section of the blade of an upper leaf (x35). 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. 11] INFOLDING OF LEAVES 25 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 in- rolling (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. Alopecurus. Psamma. Glyceria fluitans. Aira ceespitosa. Keeleria. Lolium. Festuca elatior. Cynosurus (Fig. 16). Festuca Myurus (var. sctwroides). Agrostis. 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. 26 KEELED AND HAIRY GRASSES [cH. In some grasses the tissue over the mid-rib is con- siderably 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. muritima). 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,—eg. 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). Hordeum. Molinia ccerulea. Anthoxanthum. Brachypodium sylvaticwm. Avena flavescens (Fig. 10). Agropyrum (variable). A, pubescens. Bromus asper. Triodia, B. mollis. Keleria. To a less extent. Festuca scturoides (on ribs). Melica. 11] HABITATS 27 Grasses as a rule are devoid of strong scents? or tastes, but Anthoranthum 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. Spar- tina 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. Tn the following list “ pasture-grass” (P) means useful for grazing, and “meadow-grass” (M) one that is especially valuable fur mowing—ie. 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) ZB. sterites (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. 1 The most marked exceptions are the lemon-scented grasses (especi- ally Andropogon) of India and Ceylon. 28 SHADE- AND AQUATIC-GRASSES [cH. (P and M) Loliwm perenne (meadow, pasture and waste places). (P and M) JZ. ttalicwm (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)