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(Sedge family), Juncaceae (Rush family), and some other monocotyledons with inconspicuous Howers. Singularly enough, the sexual system of Linnaeus (173 5) served to mark off more distinctly the true grasses from these allies, since very nearly all of the former then known fell under his Triandria Digynia, whilst the latter found themselves under his other classes and orders. I. STRUCTURE.-The general type of true grasses is familiar in the cultivated cereals of temperate climates-wheat, barley, rye, oats, and in the smaller plants which make up pastures and meadows and form a principal factor of the turf of natural downs. Less familiar are the grains of warmer climates-rice, maize, millet and sorgho, or the sugar-cane. Still farther removed are the bamboos of the tropics, the columnar stems of which reach to the height of forest trees. All are, however, formed on a common plan.-Root.—Most

cereals and many other grasses are annual, and possess a tuft of very numerous slender root-fibres, much branched and of great length. The majority of the members of the family are of longer duration, and have the roots also fibrous, but fewer, thicker and less branched. In such cases they are very generally given off from just above each node (often in a circle) of the lower part of the stem or rhizome, perforating the leaf-sheaths. In some bamboos they are very numerous from the lower nodes of the erect culms, and pass downwards to the soil, whilst those from the upper nodes shrivel up and form circles of spiny fibres. Stem.-The underground stem or rootstock (rhizome) of perennial grasses is usually well developed, and often forms very

FIG. I.-Rhizome of Bamboo. A, B, C, D, successive series of axes, the last bearing aerial culms. Much reduced. long creeping or subterranean rhizomes, with elongated inter nodes and sheathing scales; the widely-creeping, slender rhizomes in Marram-grass (Psamma), Agropyrum junceum, Elymus arenarius, and other sand-loving plants render them useful as sand-binders. It is also frequently short, with the nodes crowded. The turf-formation, which is characteristic of open situations in cool temperate climates, results from an extensive production of short stolons, the branches and the fibrous roots developed from their nodes forming the dense “ sod.” The very large rhizome of the bamboos (fig. 1) is also a striking example of “ definite ” growth; it is much branched. the short, thick, curved branches being given off below the apex of the older ones and at right angles to them, the whole forming a series of connected arched axes, truncate at their ends, which were formerly continued into leafy culms. The rhizome is always solid, and has the usual internal structure of the monocotyledonous stem. In the cases of branching just cited the branches break directly through the sheath of the leaf in Connexion with which they arise. In other cases the branches grow upwards through the sheaths which they ultimately split from above, and emerging as aerial shoots give a tufted habit to the plants Good examples are the oat, cock's-foot (Dactylis) and other British grasses. This mode of growth is the cause of the “ tellering” of cereals, or the production of a large number of erect growing branches from the lower nodes of the young stem. Isolated tufts or tussocks are also characteristic of steppe-and savanna-vegetation and open places generally in the warmer parts of the earth. T

The aerial leaf-bearing branches (culms) are a characteristic feature of grasses. They are generally numerous, erect, cylindrical (rarely flattened) and conspicuously jointed with evident nodes. The nodes are'solid, a strong plate of tissue passing across the stem, but the inter nodes are commonly hollow, although examples of completely solid stems are not uncommon (e.g. maize, many Andropogons, sugar-cane). The swollen nodes are a characteristic feature. In wheat, barley and most of the British native grasses they are a development, not of the culm, but of the base. of the leaf-sheath. The function of the nodes is to raise again culms which have become bent down; they are composed of highly t urges cent tissue, the cells of which elongate on the side next the earth when the culm is placed in a horizontal or oblique position, and thus raise the culm again to an erect position. The inter nodes continue to grow in length, especially the upper ones, for some time; the increase takes place in a zone at the extreme base, just above the node. The exterior of the culms is more or less concealed by the leaf-sheaths; it is usually smooth and often highly polished, the epidermal cells containing an amount of silica sufficient to leave after burning a distinct skeleton of their structure. Tabasheer is a white substance mainly composed of silica, found in the joints of several bamboos. A few of the lower inter nodes may become enlarged and sub globular, forming nutriment-stores, and grasses so characterized are termed “ bulbous ” (Arrhenatherum, Poo bulbosa, &c.). In internal structure grass-culms, save in being hollow, conform to that usual in monocotyledons; the vascular bundles run parallel in the inter nodes, but a horizontal interlacement occurs at the nodes. In grasses of temperate climates branching is rare at the upper nodes of the culm, but it is characteristic of the bamboos and many tropical grasses. The branches are strictly distichous. In many bamboos they are long and spreading or drooping and copiously ramified, in others they are reduced to hooked spines. One genus (Dinochloa, a native of the Malay archipelago) is scandent, and climbs over trees 100 ft. or more in height, Olyra latifalia, a widely-spread tropical species, is also a climber on a humbler scale. Grass-culms grow with great rapidity, as is most strikingly seen in bamboos, where a height of over 100 ft. is attained in from two to three months, and many species grow two, three or even more feet in twenty-four hours. Silicic hardening does not begin till the full height is nearly attained. The largest bamboo recorded is 170 ft., and the diameter is usually reckoned at about 4 in. to each 50 ft.

Leaves- These present special characters usually sufficient for ordinal determination. They are solitary at each node and arranged in two rows, the lower often crowded, forming a basal tuft. They consist of two distinct portions, the sheath and the blade. The sheath is often of great length, and generally completely surrounds the culm, forming a firm protection for the inter node, the younger basal portion of which, including the zone of growth, remains tender for some time. As a rule it is split down its whole length, thus differing from that of Cyperaceae which is almost invariably (Eriospom is an exception) a complete tube; in some grasses, however (species of Poa, Bromus and others), the edges are united. The sheaths are much dilated in Alopecurus wginatus and in a species of Potamochloa, in the latter, an East Indian aquatic grass, serving as floats. At the summit of 'the sheath, above the origin of the blade, is the ligule, a usually membranous process of small size (occasionally reaching r in. in length) erect and pressed-around the culm. It is rarely quite absent, but may be represented by a tuft of hairs (very conspicuous in Paricma). It serves to prevent rain-water, which has run down the blade, from entering the sheath. Melica uniflora has in addition to the ligule, a green erect tongue-like process, from the line of junction of the edges of the sheath.

The blade is frequently wanting or small and imperfect in the basal leaves, but in the rest is long and set on to the sheath at an angle. The usual form is familiar-sessile, more or less ribbon-shaped, tapering to a point, and entire at the edge. The chief modifications are the articulation of the deciduous blade on to the sheatli, which occurs in all the Bambuseae (except Planotia) and in S parlina stricla; and the interposition of a petiole between the sheath and the blade, as in bamboos, Leptaspis, Pharus, Pariaua, Lophatherum and others. In the latter case the leaf usually becomes oval, ovate or even cordate or sagittate, but these forms are found in sessile leaves also (Olyra, Panicum). The venation is strictly parallel, the midrib usually strong, and the other ribs more slender. In Anomochloa there are several nearly equal ribs and in some broad-leaved grasses (Bambuseae, Pharus, Leptaspis) the venation becomes Ill

0 » U »

£'§ '5E'° i; %q5V%

FIG. 2.-Magnified transverse section of one-half of a leaf-blade of Festuca rubfa. The dark portions represent supporting and conducting tissue; the upper face bears furrows, at the bottom of each of which are seen the motor cells m.

tessellated by transverse

connecting veins. The

tissue is often raised

above the veins, forming

longitudinal ridges,

generally on the upper

face; the stomata are in

lines in the intervening

furrows. The thick prominent

veins in Agrapyrum

occupy the whole

so in Anthoxanthum (fig. 7) and in two anomalous genera, Anomochloa and Streptochaeta.

In immediate relation with the flower itself, and often entirely concealing it, is the palea or pale (“ upper pale ” of most systematic agrostologists). This organ (fig. 15, I) is peculiar to grasses ¢ Tir ii). /li/4 'i

Q ., .» ' W . f. E. . "r, ,/ ” My il "é W/ 1 ii

t' 'Xi

, .,1

f


ii A li, if

FIG. 5.-Spikelet of Briza. FIG. 6.-Spikelet of Triticum. (Both enlarged.)

among Glumiflorae (the series to which belong the two families Gramineae and Cyperaceae), and is almost always present, certain Oryzeae and Phalarideae

upper surface of the leaf. Epidermal appendages are rare, the most frequent being marginal, saw-like, cartilaginous teeth, usually minute, but occasionally . (Dzmthonia scabra, Panicum serralum) so large as to give the margin a serrate appearance. The leaves are occasionally woolly, as in Alopecurus lanatus and one or two Panicums. The blade is often twisted, frequently so much so that the upper and under faces become reversed. In dry-country grasses the blades are often folded on the midrib, or rolled up. The rolling is effected by bands of large wedge-shaped cells-motor-cells-between the nerves, the loss of turgescence by which, as the air dries, causes the blade to curl towards the face on which they occur. The rolling up acts as a protection from too great loss of water, the exposed surface being specially protected to this end by a strong Cuticle, the majority or all of the stomata occurring on the protected surface. The stiffness of the blade, which becomes very marked in dry-country grasses, is due to the development of girders of thick-walled mechanical tissue which follow the course of all or the principal veins (fig. 2). Inflorcsccnce.-This possesses an exceptional importance in grasses, since, their Horal envelopes being much reduced and the sexual organs of very great uniformity, the characters employed for classification are mainly derived from the arrangement of the flowers and their investing bracts. Various interpretations have been given to these glumaceous organs and different terms employed for them by various writers. It may, however, be /r

)A 1/ ,

f .t, I.

fi . ' ii I l /
y» !1L' W '~   ill# N  / f I

I ., A - / , / .fy .

/' .. viii il; I, ,

  f    ¢ IN, V/   l  =

FIG. 3.-One-flowered FIG. 4.-Two-flowered spikelet spikelet of A groslis. of Aim.

b, Barren glumes; f, flowering glumes. (Both enlarged.) considered as settled that the whole of the bodies known as glumes and paleae, and distichously arranged externally to the flower, form no part of the floral envelopes, but are of the nature of bracts. These are arranged so as to form spike lets (locustae), and each spikelet may contain one, as in Agrostis (fig. 3) two, as in Aim (fig. 4) three, or a great number of flowers, as in Briza (fig. 5) Triticum (fig. 6); in some species of Erugrostis there are nearly 6o. The flowers are, as a rule, placed laterally on the axis(rachilla)of the spikelet, but in one-flowered spike lets they appear to be terminal, and are probably really being the only exceptions. It is of thin membranous consistence,

usually obtuse, often bifid, and possesses no central rib or nerve, but has two lateral ones, one on either side; the margins are frequently folded in at the ribs,

which thus become placed at the

sharp angles. This structure was formerly regarded as pointing to the fusion of two organs, and

the pale was considered by

Robert Brown to represent two

portions soldered together of a

trimerous perianth - whorl, the

third portion being the “lower

pale.” The pale is now generally considered to represent the

single bracteole, characteristic of Monocotyledons, the binerved

ia ff)

i

ft”

4 " F(

»//, ..., 'i

// '

I f' /I “ I

I I it / F fri

ll/

T .

 JM,

i'(II, f/

W ", :/,

g

FIG. 7.-Spikelet of Anthoxanthum (enlarged) without the

two lower barren glumes, showing the two upper awned barren

glumes (g) and the flower.

structure being the result of the pressure of the axis of the spikelet during the development of the pale, as in Iris and others. The flower with its pale is sessile, and is placed in the axil of another bract in such a way that the pale is exactly opposed to it, though at a slightly higher level. It is this second bract or flowering glume which has been generally called by systematists the “ lower pale, ” and with the “ upper pale ” was formerly considered to form an outer floral envelope (“ calyx, ” Jussieu; “ perianthium, ” Brown). The two bracts are, however, on different axes, one secondary to the other, and cannot therefore be parts of one whorl of organs. They are usually quite unlike one another, but in some genera (e.g. most Festuceae) are very similar in shape and appearance. The flowering glume has generally a more or less boat-shaped form, is of firm consistence, and possesses a well-marked central midrib and frequently several lateral ones. The midrib in a large proportion of genera extends into an appendage termed the own (fig. 4), and the lateral veins more rarely extend beyond the glume as sharp points (e.g. Pappophorum). The form of the flowering glume is very various, this organ being plastic and extensively modified in different genera. It frequently extends downwards a little on the rachilla, forming with the latter a swollen callus, which is separated from the free portion by a furrow. In Leptaspis it is formed into a closed cavity by the union of its edges, and encloses the flower, the styles projecting through the pervious summit. Valuable characters for distinguishing genera are obtained from the awn. This presents itself variously developed from a mere subulate point to an organ several inches in length, and when complete (as in Andropngoneae, Aveneae and Stipeae) consists of two well-marked portions, a lower twisted part and a terminal straight portion, usually set in at an angle with the former, sometimes trifid and occasionally beautifully feathery (fig. 8). The lower part is most often suppressed, and in the large group of the Pauiceae awns of- any sort are very rarely seen. The awn may be either terminal or may come off from the back of the flowering glume, and Duval ]ouve's observations have shown that it represents the blade of the leaf of which the portion of the flowering glume below its origin is the sheath; the twisted part (so often suppressed) corresponds with the petiole, and the portion of the glume extending beyond the origin of - the awn (very long in some species, e.g. of Danthonia) with the ligule of the developed foliage-leaf. When terminal the awn has three fibro-vascular bundles, when dorsal only one; it is covered with stornate-bearing epidermis. ~ The flower with its palea is thus sessile in ' the axil of a odoriferous glume, and in a few grasses (Leersia (fig. 9), Coleanthus, N ardus) the spikelet consists of nothing more, but usually (even in uniflorous spike lets) other

42 l.

W E Z /

'f

3

§ , glumes are present. Of these the two placed § Y distichously opposite each other at the base Q; of the spikelet never bear any flower in their / axils, ' and are called the empty or barren

¢ Q gr

fr

/ 5 g. | /

glumes (figs. 3, 8). They are the “ glumes ”

/ of most writers, and together form what 5 was called the “gluma” by R. Brown. /, They rarely differ much from one another, ~, but one may be smaller or quite absent (Panicum, Setaria (fig. Io), Paspalum, Lolium), or both be altogether suppressed, as above noticed. They are commonly firm and strong, often enclose the spikelet, and are rarely provided with long points or imperfect awns. Generally speaking they do not share in the special modifications of the flowering glumes, and rarely themselves undergo modification, chiefly in hardening of portions (Sclerachne, M anisuris, Anthef h R 1 . 4 ' P / it ' ' . » if i ' 'Q

'  ' Tj' .

»~ l ., f P If “ b ' A (pa) . .M, | § , mill M q rl? / / Fm. 8.-Spikelet of Q ll ' y, , ,, ..» f b Stipa pennala. The pair " “ . /4 of barren glumes (b) b rv# are separated from the flowering glume, which bears a long awn, twisted below the knee and feathery above. About % nat. size. F I G. 9.- Spikelet of Leer-FIG. 10.-Spikelet of Setaria, with an abortive sia. f, Flower- branch (h) beneath it. b, Barren glumes; f, flowering glume; p, pale. ing glume; p, pale. phora, Peltophorum), so as to afford greater protection to the flowers or fruit. But it is usual to find, besides the basal glumes, a few other empty ones, and these are in two- or more-flowered spike lets (see Triticum, fig. 6) at the top of the rhachilla (numerous in Lophatherum), or in uniflorous ones (fig. ro) below and interposed between the floral glume and the basal pair. " The axis of the spikelet is frequently jointed and breaks up into articulations above each flower. Tufts or borders of hairs are frequently present (Calamagrostis, Phragmites, Andropogon), and are often so long as to surround 'and conceal the flowers (fig. 11). The axis is often continued beyond the last flower or glume as ia bristle or stalk. I nvolucres or organs outside the spike lets also occur, and are formed in various ways. Thus in Setaria (fig. ro), Pennisetum, &c., the one or more circles of simple or feathery hairs represent abortive branches of the inflorescence; in Cenchrus (fig. 12) these become consolidated, and the inner ones flattened so as to form a very hard globular spiny case to the spike lets. The cup-shaped involucre of Cornucopia is a dilatation of the axis into a hollow receptacle with a raised border. In Cynasurus (Dog's tail)

the pectin ate involucre which conw ma { ' W J *

 , zz,  /4.

d ¥». > ~» 'ceals the spikelet is a barren or " V abortive spikelet. Bracts of a more ' l:Q§ iif'§ f ff general character subtending branches C" ' of the inflorescence are singularly rare in Gramineae, in marked con- d' ~'b

    ivawx ll W d

1 if lv flfl ll /if l/ Ll.

 W  I

st f f trast with Cyperaceae, where they are so conspicuous. They however occur in a whole section of Audropagon, in Anomochloa, and at the base of the spike in Sesleria. The remarkable ovoid involucre of Coix, which becomes of stony hardness, white and polished (then known as “ ]ob's tears, ” q.v.), is also a modiied bract or leaf-sheath. It is closed except at the apex, and contains the female a, b, c, c, (Z FIG. 1 1 -Spikelet of Reed (Phragmites communis) opened out. Barren glumes. Fertile glumes, each enclosing one flower with its pale d. Note the zigzag axis (rhachilla) bearing long silky hairs. spikelet, the stalks of the male inflorescence and the long styles emerging, through the small apical orifice. Any number of spike lets may compose the inflorescence, and their arrangement is very various. In the spicate forms, with sessile spike lets on the main axis, the latter is often dilated and flattened (Paspalum), or is more or less thickened and hollowed out (Sienotaphrum, Roltboellia, Tripsacum), when the spike lets are sunk and buried within the cavities. Every variety of racemose and paniculate inflorescence obtains, and the number of spike lets composing those of the large kinds is often immense. Rarely the inflorescence consists of very few flowers; thus Lygeum Spartum, the most anomalous of European grasses, has but two or three large uni/. ” if E / g&' p AQW 3 §§ ;€§ ~§ lifgff ul I FIG. 12.-Spikelet of Cenchrus echinatus enclosed in a bristly involucre. florous spike lets, which are fused together at the base, and have no basal glumes, but are enveloped in a. large, hooded, spathe-like bract. Flower.-This is characterized by remarkable uniformity. The perianth is represented by very rudimentary, small, fleshy scales arising below the ovary, called lodicules; they are elongated ffl , f*1 "W 9/ 3 l ff(

  • >:'* l?"*”' ' ll(

lb /f}f;~', , , , // t 31 FIG. 13.-Flowers of Grasses (enlarged). 1, Piptatherum, with the palea p; 2, Poa; 3, Oryza; Z, Lodicule. or truncate, sometimes fringed with hairs, and are in contact with the ovary. Their usual number is two, and they are placed collaterally at the anterior side of the flower (fig. 13,) that is, within the flowering glume. They are generally considered to represent the inner whorl of the ordinary monocotyledonous as bisexual flowers

(liliaoeous) perianth, the outer whorl of these being suppressed as well as the posterior member of the inner whorl. This latter is present almost constantly in Stipeae and Bambuseae, which have three lodicules, and in the latter group they are occasionally more numerous. In Anomochloa they are represented by hairs. In Slreptochaela there are six lodicules, alternately arranged in two whorls. Sometimes, as in Anthoxanthum, they are absent. In M elica there is one large anterior lodicule resulting presumably from the union of the two which are present in allied genera. Professor E. Hackel, however, regards this as an undivided second pale, which in the majority of the grasses is split in halves, and the posterior lodicule, when present, as a third pale. On this view the grass-flower has no perianth. The function of the lodicules is the separation of the pale and glume to allow the protrusion of stamens and stigmas; they effect this by swelling and thus exerting pressure on the base of these two structures. Where, as in Anlhoxanlhum, there are no lodicules, pale and glume do not become laterally separated, and the stamens and stigmas protrude only at the apex of the floret (fig. 7). Grass-flowers are usually hermaphrodite, but there are very many exceptions. Thus it is common to find one or more imperfect (usually male) flowers in the same spikelet with bisexual ones, and their relative position is important in classification. H olcus and Arrhenatherum are examples in English grasses; and as a rule in species of temperate regions separation of the sexes is not carried further. In warmer countries monoecious and dioecious grasses are more frequent. In such cases the male and female spike lets and inflorescence may be very dissimilar, as in maize, ]ob's tears, Euclzlaena, Spinzfex, &c.; and in some dioecious species this dissimilarity has led to the two sexes being referred to different genera (e.g. An!/zephora axilli/Zora is the female of Buchloe dactylnides, and Neu/achne paradoxa of a species of Spimfex). In other grasses, however, with the sexes in different plants (ag. Brizopyrum, Dislichlis, ,Eragrostis capilalag Gynerium), no such dimorphism obtains. Amphicarpum is remarkable in having c leis toga mic flowers borne on long radical subterranean peduncles which are fertile, whilst the conspicuous upper paniculate ones, though apparently perfect, never produce fruit. Something similar occurs in Leersia oryzoides, where the fertile spike lets are concealed within the leaf-sheaths. Androecium.-In the vast majority there are three stamens alternating with the lodicules, and therefore one anterior, i.e. opposite the flowering glume, the other two being posterior and in contact with the palea (fig. 13, 1 and 2). They are hypo-

gynous, and have long and very delicate filaments, and large, linear or oblong two-celled anthers, dorsifixed and ultimately very versatile, deeply' indented at each end, and commonly exserted and pendulous. Suppression of the anterior stamen sometimes occurs (e.g. Anthoxanlhum, f1g. 7), or the two posterior ones may be absent (U niola, Cinna, Phippsia, Festuca bromides). There is in some genera (Oryza, most Bambuseae) another row of three stamens, making six in all (fig. 13, 3); and Anomochloa and T elrarrhena possess four. The stamens become numerous (ten to forty) in the male flowers of a few monoecious genera (Pariana, Lusiola). In Ochlandra they vary from seven to thirty, and in Giganlochloa they are monadelphous.

G ynoecium.-The pistil consists of a single carpel, opposite the pale in the median plane of the spikelet. The ovary is small, rounded to elliptical, and one-celled, and contains a single slightly bent ovule sessile on the ventral suture (that is, springing from the back of the ovary); the micropyle points downwards. It bears usually two lateral styles which are quite distinct or connate at the base, sometimes for a greater length (fig. 14, 1), each endsin a densely hairy or feathery stigma (fig. 14). Occasionally there is but a single style, as in Nardus (fig. 14, 7), which corresponds to the midrib of the carpel. The very long and apparently simple stigma of maize arises from the union of two. Many of the bamboos have a third, anterior, style. Comparing the flower of Gramineae with the general monocotyledonous plan as represented by Liliaceae and other families (fig. 1 5), it will be seen to differ in the absence of the outer row and the posterior member of the inner row of the perianth-leaves, of the whole inner row of stamens, and of the two lateral carpels, ip Q .|'/r f, V/ f H N

ilillili' Eilu ff(ll

“l 3 fly/

1,1 X | . l-tf

is yy lil i 2 § H'j lly

3 ' l . , ffl % ./

  • § ' *lj W . ~ lf/

§ A§ , I, , awe-KV /A, ,

raw, /= ',

tw Tc' l' » ' ' 5

sv? /~ .

!' ~ '¥? -5>l?2 ll

iii?

, /f -' f

e

f

ll f,

4 5 up ui, ”/R M

FIG. 14.-Pistils of Grasses (much enlarged). 1, Alopecurus; 2 Brpérzug; 3, Arrhenatherum; 4, Glyceria; 5, Melina; 6, Mibora; 7, ar us.

whilst the remaining members of the perianth are in a rudimentary cpndilgionf Biét each or any of the usually missing organs are o e oun .w

normally in differ- Oa

ent genera, or as ',

occasional develop- * }, , of ° - ', , ff.~j§ 3§ fj{ ments. 4 9 ff, ” ' '-§ :l,

P0zz rnm0n.- J V, 'rig, M 'f

Grasses are gener- ~ * . '&l-§ -:, y, / ally wind - pollin- ¢ 1, - —' ./

ated, though self- 1 &{ 2

fertilization sometimes occurs.

Afew

species, as we have

seen, are mono-FIG.

15.-Diagrams of the ordinary Grassflower 1, Actual condition;

2, Theoretical, with

d

Outer row of perianth

leaves.

ecious or dioecious, the suppressed e, Inner row. While many are irganssupplied. f, Opter row of Gr, XIS. S ZITIEHS.

polygalmfus (havmg b, Flowering glume. g, lnner row. umsexua 35 We c, Palea. h, Pistil.

as in many members of the tribes Amiropoganeae, fig. 18, and Paniceae), and in these the male flower of a spikelet always blooms later than the hermaphrodite, so that its pollen can only effect cross-fertilization upon other spike lets in the same or another plant. Of those with only bisexual flowers, many are strongly protogynous (the stigmas protruding before the anthers are ripe), such as Alopecurus and Anthoxanthum (Hg. 7), but generally the anthers protrude first and discharge the greater part of their pollen before the stigmas appear. The filaments elongate rapidly at flowering-time, and the lightly versatile anthers empty an abundance of finely granular smooth pollen through a longitudinal slit. Some flowers, such as rye, have lost the power of effective self-fertilization, but in most cases both forms, self- and cross-fertilization, seem to be possible. Thus the species of wheat are usually self fertilized, but cross-fertilization is possible since the glurnes are open above, the stigmas project laterally, and the anthers empty only about one-third of their pollen in their own flower and the rest into the air. In some cultivated races of barley, cross fertilization is precluded, as the flowers never open. Reference has already been made to c leis toga mic species which occur in several genera.,

Fruit and Seed.-The ovary ripens into a usually small ovoid or rounded fruit, which is entirely occupied by the single large seed, from which it is not to be distinguished, the thin pericarp being completely united to its surface. To this peculiar fruit the term caryopsis has been applied (more familiarly “grain ”); it is commonly furrowed longitudinally down one side (usually the inner, but in Coix and its allies, the outer), and an additional covering is not infrequently provided by the adherence of the persistent palea, or even also of the flowering glume (“ chaff ” of cereals). From this type are a few deviations; thus in S porobolus, &c. (fig. 16), the pericarp is not united with the seed but is quite distinct, dehisces, and allows the loose seed to escape. Sometimes the pericarp is membranous, sometimes hard, forming a nut, as in some genera of Bambuseae, while in other Bambuseae it becomes thick and fleshy, forming a berry often as large as an apple. In M elocamw the berry forms an edible fruit 3 or 4 in. long, with a pointed i'., ;f'r/ beak of 2 in. more; it is indehiscent, and the "mg small seed germinates whilst the fruit is still attached to the tree, putting out a tuft of roots and a shoot, and not falling till the latter is 6 in. long. The position of the embryo is plainly visible on the front side at the base of the grain. On the other, posterior, side of the grain is a more or less evident, sometimes punctiform, sometimes elongated or linear mark, the hilum, the place where the ovule was fastened to the wall of the ovary. The form of the hilum is constant throughout a genus, and sometimes also in whole tribes.

The testa is thin and membranous but occasionally coloured, and the embryo small, the great bulk of the seed being occupied by the hard farinaceous endosperm (albumen) on which the nutritive value of the grain depends. The outermost layer of endosperm, the aleuron-layer, consists of regular cells filled with small proteid granules; the rest is made up of large polygonal cells containing numerous starch-grains in a matrix of proteid which may be continuous (horny endosperm) or granular (mealy endosperm). The embryo presents many points of interest. Its position is remarkable, closely applied to the surface of the endosperm at the' base of its outer side. This character is absolute for the whole order, and effectually separates Gramineae from Cyperaceae. The part in contact with the endosperm is plate-like, and is known as the scutellum; the surface in contact with the endosperm forms an absorptive epithelium. In some grasses there is a small scale-like appendage opposite the scutellum, the epiblasl. There is some difference of opinion as to which structure or structures represent the cotyledon. Three must be considered: (1) the scutellum, connected by vascular tissue with the vascular cylinder of the main axis of the embryo which it more or less envelops; it never leaves the seed, serving merely to prepare and absorb the food-stuff in the endosperm; (2) the cellular outgrowth of the axis, the epiblast, small and inconspicuous as in wheat, or larger as in Stipa; (3) the pileole or germ-sheath, arising on the same side of the axis and above the scutellum, enveloping the plumule in the seed and appearing above ground as a generally colourless sheath from the apex of which the plumule ultimately breaks (fig. r7,4, b). The development of these structures (which was investigated by van Tieghem), FIG. 16.-

Fruit ofSporobolus,

showing

the dehiscent

pericarp and

seed.

5 .

~ .- "" I ' //V, /iii

73/' 'IM, 5, = B

if ltll

ll :M /, ,' if { ig,

  • wif . i 1 Fl °

if l 2 '-. if/uf 5 0 5

FIG. 17.-A Grain of Wheat. I, back, and 2, front view; 3, vertical section, showing (b) the endosperm, and (a) embryo; 4, beginning of germination, showing (17) the pileole and (c) the radicle and secondary rootlets surrounded by their coleorrhizae. especially in relation to the origin of the vascular bundles which supply them, favours the view that the scutellum and pileole are highly differentiated parts of a single cotyledon, and this view is in accord with a comparative study of the seedling of grasses and of other monocotyledons. The epiblast has been regarded as representing a second cotyledon, but this is a very doubtful interpretation.

Germination.-In germination the coleorhiza lengthens, nxptures the pericarp, and nxes the grain to the ground by developing numerous hairs. The radicle then breaks through the coleorhiza, as do also the secondary rootlets where, as in the case of many cereals, these have been formed in the embryo (fig. 17, 4). The germ-sheath grows vertically upwards, its stiff apex pushing through the soil, while the plumule is hidden in its hollow interior. Finally the plumule escapes, its leaves successively breaking through at the tip of the germ-sheath. The scutellum meanwhile feeds the developing embryo from the endosperm. The growth of the primary root is limited; sooner or later adventitious roots develop from the axis above the radicle which they ultimately exceed in growth. Means of Distribution.-Various methods of scattering the grain have been adopted, in which parts of the spikelet or inflorescence are concerned. Short spikes may fall from the culm as a whole; or the axis of a spike or raceme is jointed so that one spikelet falls with each joint as in many Andropogoneae and H ordeae. In many-flowered spike lets the rachilla is often jointed and breaks into as many pieces as there are fruits, each piece bearing a glume and pale. One-flowered spike lets may fall as a whole (as in the tribes Paniceae and Andropogoneae), or the axis is jointed above the barren glumes so that only the flowering glume and pale fall with the fruit. These arrangements are, with few exceptions, lacking in cultivated cereals though present in their Wild forms, so far as these are known. Such arrangements are disadvantageous for the complete gathering of the fruit, and therefore varieties in which they are not present would be preferred for cultivation. The persistent bracts (glume and pale) afford an additional protection to the fruit; they protect the embryo, which is near the surface, from too rapid wetting and, when once soaked, from drying up again. They also decrease the specific gravity, so that the grain is more readily carried by the wind, especially when, as in Briza, the glume has a large surface compared with the size of the grain, or when, as in Holcus, empty glumes also take part; in Canary grass (Phalaris) the large empty glumes bear a membranous wing on the keel. In the sugar-cane (Saccharum) and several allied genera the separating joints of the axis bear long hairs below the spike lets; in others, as in Arundo (a reed-grass), the flowering glumes are enveloped in long hairs. The awn which is frequently borne on the flowering glume is also a very efficient means of distribution, catching into fur of animals or plumage of birds, or as often in Stipa (fig. 8) forming a long feather for wind carriage. In Tragus the glumes bear numerous short hooked bristles. The fleshy berries of some Bambuseae favour distribution by animals.

The awn is also of use in burying the fruit in the soil. Thus in Stipa, species of Avena, Heteropogon and others the base of the glume forms a sharp point which will easily penetrate the ground; above the point are short stiff upwardly pointing hairs which oppose its withdrawal. Thelong awn, which is bent and closely twisted below the bend, acts as a driving organ; it is very hygroscopic, the coils untwisting when damp and twisting up when dry. The repeated twisting and untwisting, especially-y when.the upper part of the awn has become fixed in the earth or caught in surrounding vegetation, drives the point deeper and deeper into the ground. Such grasses often cause harm to sheep by catching in the wool and boring through the skin.

A peculiar method of distribution occurs in some alpine and arctic grasses, which grow under conditions where ripening of the fruit is often uncertain. The entire spikelet, or single flowers, are transformed into small-leaved shoots which fall from the axes and readily root in the ground. Some species, such as Poa stricta, are known only in this viviparous condition; others, like our British species Festuca ovina and Poa alpina, become viviparous under the special climatic conditions.

II. CLASsIFICATION.-Gramineae are sharply defined from all other plants, and there are no genera as to which it is possible to feel a doubt whether they should be referred to it or not. The only family closely allied is Cyperaceae, and the points of difference between the two may be here brought together. The best distinctions are found in the position of the embryo in relation to the endosperm—lateral in grasses, basal in Cyperaceae —and in the possession by Gramineae of the 2-nerved palea below each flower. Less absolute characters, but generally trustworthy and more easily observed, are the feathery stigmas, the always distichous arrangement of the glumes, the usual absence of more general bracts in the inflorescence, the split leaf-sheaths, and the hollow, cylindrical, jointed culms-some or all of which are wanting in all Cyperaceae. The same characters will distinguish grasses from the other glumiferous orders, Restiaceae, and Eriocaulonaceae, which are besides further removed by their capsular fruit and pendulous ovules. To other monocotyledonous families the resemblances are merely of adaptive or vegetative characters. Some Commelinaceae and Marantaceae approach grasses in foliage; the leaves of Allium, &c., possess a ligule; the habit of some palms reminds one of the bamboos; and Iuncaceae and a few Liliaceae possess an inconspicuous scarious perianth. There are about goo genera containing about 3500 well-defined species. The great uniformity among the very numerous species of this vast family renders its classijicalizm very difficult. The difficulty has been increased by the confusion resulting from the multiplication of genera founded on slight characters, and from the description (in consequence of their wide distribution) of identical plants under several different genera.

No characters for main divisions can be obtained from the flower proper or fruit (with the exception of the character of the hilum), and it has therefore been found necessary to trust to characters derived from the usually less important inflorescence and bracts.

Robert Brown suggested two primary divisions-Paniceae and Poaceae, according to the position of the most perfect Bower in the spikelet; this is the upper (apparently) terminal one in the HISI, whilst in the second it occupies the lower position, the more imperfect ones (if any) being above it. Munro supplemented this by another character easier of verification, and of even greater constancy, in the articulation of the pedicel in the Paniceae immediately below the glumes; whilst in Poaceae this does not occur, but the axis of the spikelet frequently articulates above the pair of empty basal glumes. Neither of these great divisions will well accommodate certain genera allied to Phalaris, for which Brown proposed tentatively a third group (since named Phalarideae); this, or at least the greater part of it, is placed by Bentham under the Poaceae. The following arrangement has been proposed by Professor Eduard Hackel in his recent monograph on the order. A. Spikelets one-flowered, rarely two-flowered as in Zea, falling from the pedicel entire or with certain joints of the rachis at maturity. Rachilla not produced beyond the flowers. a. Hilum a point; spike lets not laterally compressed. a Fertile-glume and pale hyaline; empty glumes thick, membranous to coriaceous or cartilaginous, the lowest the largest. Rachis generally jointed and breaking up when mature.

I. Spikelets uni sexual, male and female in separate infiorescences or on different parts of the same inflorescence. 1. Maydeae.

2. Spikelets bisexual, or male and bisexual, each male standing close toabisexual. 2. Andropogoneae. B Fertile glume and pale cartilaginous, coriaceous or papery; empty glumes more delicate, usually herbaceous, the lowest usually smallest. Spikelets falling singly from the unjointed rachis of the spike or the ultimate branches of the panicle. 3. Paniceae.

b. Hilum a line; spike lets laterally compressed. 4. Oryzeae.

B. Spikelets one- to indefinite-flowered; in the one-flowered the rachilla frequently produced beyond the flower; rachilla generally jointed above the empty glumes, which remain after the fruiting glumes have fallen. hen more than one-flowered, distinct inter nodes are developed between the flowers.,

a. Culm herbaceous, annual; leaf-blade sessile, and not jointed to the sheath.

a. Spikelets upon distinct pedicels and arranged in panicles or racemes.

I. Spikolets one-flowered.

i. Empty glumes 4. 5. Phalarideae.

ii. Empty glumes 2. 6. Agrostideae.

Il. Spikelets more than one-flowered.

i. Fertile glumes generally shorter than the empty glumes, usually with a bent awn on the back. 7. Afueneae.

ii. Fertile glumes generally longer than the empty, unawned or with a straight, terminal awn.

9. Festuceae.

B Spikelets crowded in two close rows, forming a one-sided spike or raceme with a continuous (not jointed) rachis. 8. Chlofideae.

y Spikelets in two opposite rows forming an equal-sided spike. ro. Hordeae.

b. Culm woody, at any rate at the base, leaf-blade jointed to the sheath, often with a short, slender petiole. V II. Bambuseae.

Tribe I. Maydeae (7 genera in the warmer parts of the earth). Zea Mays (maize, q.v., or lndian corn) (gin). Tripsacum, 2 or 3 species in subtropical America north of the equator; Tr. dactyloides (gama grass) extends northwards to Illinois and Connecticut; it is used for fodder and as an ornamental plant. Coix Lacryma- Jobi (]ob's tears) q.'v.

Tribe 2. Andropogoneae (25 genera, mainly tropical). The spike lets are arranged in spike-like racemes, generally in pairs consisting of a sessile and stalked spikelet at each joint of the rachis (fig. 18). Many are savanna grasses, in various parts of the tropics, for instance the large genus Andfopogon, Elionurus and others. Saccharum ojicinarum (sugar-cane) (q.v.). Sorghum, an important tropical cereal known as black millet or durra (q.v.). Miscanthus and Eriunthus, nearly allied to Saccharum, arewith large silky flower-panicles, which are

grown for ornament. Impemta, another

ally, is a widespread tropical genus; one species I. arundinacea is the principal grass tall reed like grasses,

<l

l

if

of the alang-alang lields in the Malay Archipelago; it is used for thatch. Vossia, an aquatic grass, often floating, is found in .

western India and tropical Africa. In the swampy lands of the upper Nile it forms,

along with a species of Saccharum, huge floating grass barriers. Elionurus, a wide- 1 spread savanna grass in tropical and subtropical America, and also in the tropics of

the old world, is rejected by cattle probably on account of its aromatic character, the spike lets having a strong balsam-like smell. Other aromatic members are Andropogon

Nardus, a native of India, but also cultivated, the rhizome, leaves and especially the spike lets of which contain a Volatile oil, which on distillation yields the citronella oil of commerce. A closely allied species, /l. Schoenanfhus (lemon-grass), yields lemon-grass oil; FIG 13 .. Apai1-of a variety is used by the negroes in western Spikelets of And, -0-Africa for hemorrhage. Other species of pggoyh the same genus are used as stimulants and cosmetics in various parts of the tropics. The species of Heteropogvn, a cosmopolitan genus in the warmer parts of the world, have strongly awned spike lets. Themeda Forskalii, which occurs from the Mediterranean region to South Africa and Tasmania, is the kangaroo grass of Australia, where, as in South Africa, it often covers wide tracts.

Tribe 3. Paniceae (about 25 genera, tropical to subtropical; a few temperate), a second flower, generally male, rarely hermaphrodite, is often present below the fertile flower. Paspalum, is a large tropical genus, most abundant in America, especially on the pampas and campos; many species are good forage plants, and the grain is sometimes used for food. Amp/zicarpum, native in the south-eastern Unitcd States, has fertile cleistogamous spike lets on filiform runners at the base of the culm, those on the terminal panicle are sterile. Panicum, a very polymorphic genus, and one of the largest in the order, is widely spread in all warm countries; together with species of Paspalum they form good forage grasses in the South American savannas and campos. Panicum Crus-galli is a polymorphic cosmopolitan grass, which is often grown for fodder; in one form (P. frumenlaceum) it is cultivated in India for its grain. P. plicatum, with broad folded leaves, is an ornamental greenhouse grass. P. miliaceum is millet (q.1/.), and P. altissimum, Guinea grass. In the closely allied genus Digitaria, which is sometimes' regarded as a section of Panicum, the lowest 'barren glume is reduced to a point; D. sanguinalis is a very widespread grass, in Bohemia it is cultivated as a food-grain; it is also the crab-grass of the southern United States, where it is used for fodder.

In Setaria and allied genera the spikelet is subtended by an involucre of bristles or spines which represent sterile branches of the inflorescence. Sefaria italica, Hungarian grass, is extensively grown as a food-grain both in China and Japan, parts of India and western Asia, as well as in Europe, where its culture dates from prehistoric times; it is found in considerable quantity in the lake dwellings of the Stone age.

In Cenchrus the bristles unite to form a tough spiny capsule if gl/

if

/I / fig. I2); C. tribuloides (bur-grass) and other species are troublesome weeds in North an'd South America, as the involucre clings to the wool of sheep and is removed with great difficulty. Pennisetum typhoideum is widely cultivated as a grain in tropical Africa. Spinifex, a dioecious grass, is widespread on the coasts of Australia and eastern Asia, forming an important sand-binder. The female heads are spinose with long pungent bracts, fall entire when ripe and are carried away by wind or sea, becoming finally anchored in the sand and falling to pieces.

Tribe 4. Oryzeae (16 genera, mainly tropical and subtropical). The spike lets are sometimes uni sexual, and there are often six stamens. Leersia is a genus of swamp grasses, one of which L. oryzoides occurs in the north temperate zone of both old and new worlds, and is a rare grass in Surrey, Sussex and Hampshire. Zizariia aquatiea (Tuscarora or Indian rice) is a reed-like rass growing over large areas on banks of streams and lakes in North America and north-east Asia. The Indians collect the grain for food. Oryza sativa (rice) (q.v.). Lygeum Spartumfwith a cree ing stem and stili rushlike leaves, is common on rocky soil on the high plains bordering the western Mediterranean, and is one of the sources of esparto. Tribe 5. Phalarideae (6 genera, three of which are South African and Australasian; the others are more widely distributed, and represented in our flora). Phalarir

arundinacea, is a reed-grass found on the banks of British rivers and lakes; a variety with striped leaves known as ribbon-grass is grown for ornament. P. canariensis (Canary grass, a native of southern Europe ~- and the Mediterranean area) is grown for bird-food and sometimes as a cereal. Anthoxanthum

odoratum, the sweet vernal grassof our flora, owes its scent to the presence of coumarin, which is also present in the closely allied genus Hierorhloe (fig. 19), which occurs throughout the temperate and frigid zones.

Tribe 6. Agrostideae (about 35 genera, occurring in all parts of the world; eleven are British). Aristida and Stipa are large and widely distributed genera, occurring especially on open plains and steppes; the conspicuously awned persistent flowering glume forms an efficient means of dispersing the grain. Stipa pennata is a characteristic species of the Russian steppes. St. .vpartea (porcupine grass) and other species are plentiful on the North American prairies. St. lenacixsima is the Spanish esparto grass (q.v.), known in North Africa as halfa or alfa. Phleum has a cylindrical spike-like inflorescence; P. pretense (timothy) is a valuable fodder grass, as also is Alopecurus pratensis (foxtail). Sporobolus, a large genus in the warmer parts of both hemispheres, but chiefly America, derives its name from the fact that the seed is ultimately expelled from the fruit. Agrostis is a large world-wide genus, but especially developed in the north temperate zone, where it includes important meadow grasses. Calarnagrostis and Deyeuxia are tall, often reed-like grasses, occurring throughout the temperate and arctic zones and upon high mountains in the tropics. Ammophila arundinacea (or Psamrna arenaria) (Marram grass) with its long creeping stems forms a useful sand-binder on the coasts of Europe, North Africa and the Atlantic states of America.

Tribe 7. Aveneae (about 24 genera, seven of which are British). Holcus lanatus (Yorkshire fog, soft grass) is a common meadow and wayside grass with woolly or downy leaves. Aira is a genus of delicate annuals with slender hair-like branches of the panicle. Desehampsia and Triselum occur in temperate and cold regions or on high mountains in the tropics; T. pretense (Avena flavescens) with a loose anicle and yellow shining spike lets is a valuable fodder grass. Evena fatua is the wild oat and A. sativa the cultivated oat (q.v.). Arrheriatherum avenaeeum, a perennial field grass, native in Britain and central and southern Europe, is cultivated in North America.

Tribe 8. Chlorideae (about 30 genera, chiefly in warm countries). The only British representative is Cyrzodon Dactylori (dog's tooth, Bermuda grass) found on sandy shores in the south-west of England; it is a cosmopolitan, covering the ground in sandy soils, and forming an important forage grass in many dry climates (Bermuda grass of the southern United States, and known as durba, dub and»other names in India). Species of Chloris are grown as ornamental grasses. Bouteloua with numerous species (mesquite grass, grama grass) on the plains of the south-western United States, afford good grazing. Eleusine indica is a common tropical weed; the nearly allied species E. Coracana is a cultivated grain in the warmer parts of Asia and throughout Africa. Buchloe daetyloides is the buffalo grass of the North American prairies, a valuable fodder. Tribe 9. Festuceae (about 83 genera, including tropical, temperate, arctic and alpine forms) many are important meadow-grasses; I5 are British. Gynerium argenteum (pampas grass) is a native of southern Brazil and Argentina. Arurido and Phragmites are tall reed-grasses (see REED). Several species of Triodia cover large areas

Flo. 19.-Phalarideae. Spikelet

of Hieroehloe.

of the interior of Australia, and from their stifi, sharply pointed leaves are very troublesome. Eragrostis, one of the larger genera of the order, is widely distributed in the warmer parts of the earth; many species are grown for ornament and E. abyssinica is an important food-plant in Abyssinia.

Koeleria cristata is a

fodder-grass. Briza

media (quaking grass)

is a useful meadow grass.

Dactylis glomerata

(cock's-foot), a

perennial grass with a

dense panicle, common

in pastures and waste

places is a useful %

meadow-grass. It- has J

become naturalized ini '-North

America, where

it is known as orchard

“if e

ia;

fi” '..> I

Ky:? & 1

grass, as it will grow I/I

in shade. Cynosurus

cristatus (dog's tail) is /,

a common pasture- r,

grass. Poa, a large ' "" .

genus widely distri- 4, "

buted in temperate and “ v l Q cold countries, includes, ' ~ f (1 / ma ny meadow and 2, H " f K

alpine grasses; eight wr 5 'y fl. / species are British; P. ' ', f ll!" /, /Q , anmia (fig. 20) is the, i » '* ll L if, vs/ very common weed in

paths and waste places; “ * l' ' ' P. praterisis and P. trivial is are also common

grasses of meadows,

banks and pastures, the

former is the “ June

grass ” or “ Kentucky I

blue grass” of North Q ' fi "

America; P. alpina

is a mountain grass of

the northern hemi-sphere

and found also

in the Arctic region.

The largest species of

the genus is Poa jlabellata

which forms great

tufts 6-7 ft. high with,

of the Falkland and certain antarctic islands where it is known as tussock grass. Glyceria fluitans, manna-grass, socalled from the sweet grain, is one of the best fodder grasses for swampy meadows; the grain is an article of food in central Europe. Festuca (fescue) is also a large and widely distributed genus, but found especially in the temperate and cold zones; it includes valuable pasture grasses, such as F. ovina (sheep's fescue), F. rubra; nine species are British. The closely allied genus Brornus (brome grass) is also widely distributed but most abundant in the north temperate zone; B. erectus is a useful forage grass on dry chalky soil.

Tribe 10. Hordeae (about 19 genera, widely distributed; six are British). Nardus stricta (matwecd), found on heaths and dry pastures, is a small perennial with slender rigid stem and leaves, it is a useless grass, crowding out better sorts. Lolium perenrze, ray- (or by corruption rye-) grass, is common in waste places and a valuable pasture grass; L. italieurn is the Italian ray-grass; L. temulentum (darnel) contains a narcotic principle in the grain. Secale cereale, rye (q.1».), is cultivated mainly in northern Europe. Agropyrurri repens (couch grass) has a long creeping underground stem, and is a troublesome weed in cultivated land; the widely creeping stem of A. jimceurn, found on sandy sea-shores, renders it a useful sand-binder. Triticum sativum is wheat (q.11.) (Hg. 21), and Hordeum sativum, barley (q.v.). H. rnuriniirn, wild barley, is a common grass in waste places. Elymus 4§

. " '~ I


iarrs

& x/ if

a%Wl*§ ~i'&y

fyfgliritz J

  • iii* 1

i,

) ¢ 1

lid?

FIG. 20.-Poa aririua. Plant in Flower; about i nat. size. 1, one spikelet. leaves arranged like a fan' it is a native M

,

ix. ., g7, ,

it *ff

is a

f ni,

Q,

til

(4

arenarius (lyme grass) occurs on sandy sea-shores in the north temperate zone and is a useful sand-binder. Tribe II. Bambuseae. Contains 23 genera, mainly tropical. See BAMBOO.

FIG. 2 I .-Spike

of Wheat

(Trilieum sativurn).

About Q

III. D1srR1BUr1oN.-Grasses are the most ¥f>t-f>Z@universally diffused of all ii owe ring plants. There is no district in which they do not occur, and in nearly all they are a leading feature of the Hora. In number of species Gramineae comes considerably after Conipositae and Leguminosae, the two most numerous orders of phanerogams, but in number of individual plants it probably far exceeds either, whilst from the wide extension of many of its species, the proportion of Gramineae to other orders in the various floras of the world is much higher than its number of species would lead one to expect. In tropical regions, where Leguminosae is the leading order, grasses closely follow as the second, whilst in the warm and temperate regions of the northern hemisphere, in which Compositae takes the lead, Gramineae again occupies the second position.

While the greatest number of species is found in the tropical zone, the number of individuals is greater in the temperate zones, where they form extended areas of turf. Turf- or meadow formation depends upon uniform rainfall. Grasses also characterize steppes and savannas, where they form scattered tufts. The bamboos are a feature of tropical forest vegetation, especially in the monsoon region. As the colder latitudes are entered the grasses become relatively more numerous, and are the leading family in Arctic and Antarctic regions. The only countries where the order plays a distinctly subordinate part are some extra-tropical regions of the southern hemisphere, Australia, the Cape, Chili, &c. The proportion of graminaceous species to the whole phanerogamic flora in different countries is found to vary from nearly ith in the Arctic regions to about Qgth at the Cape; in the British Isles it is about flgth. The principal climatic cause influencing the number of graminaceous species appears to be amount of moisture. A remarkable feature of the distribution of grasses is its uniformity; there are no great centres for the order, as in Compositae, where a marked preponderance of endemic species exists; and the genera, except some of the smallest or monotypic ones, have usually a wide distribution.

The distribution of the trop1'cal tribe Bombuseae is interesting. The species are about equally divided between the Indo-Malayan region and tropical America, ” only one species being common to both. The tribe is very poorly represented in tropical Africa; one species Oxytenonthera abyssinica has a wide range, and three monotypic genera are endemic in western tropical Africa. None is recorded for Australia, though species may perhaps occur on the northern coast. One species of Arundinoria reaches northwards as far as Virginia, and the elevation attained in the Andes by some species of Chusquea is very remarkable, -one, C. aristata, being abundant from 1 5,000 ft. up to nearly the level of perpetual snow.

Many grasses are almost cosmopolitan, such as the common reed, Phragmites comrniinis; and many range throughout the warm regions of the globe, e.g. Cynodon Dactylon, Ele-usine indica, I mperata orundinacea, S porobolus indicus, Src., and such weeds of cultivation as species of Setaria, Echinochloa. Several species of the north temperate zone, such as Poo nernoralis, P. pratensis, Festuca ovina, F. rubra and others, are absent in the tropics but reappear in the antarctic regions; others (e.g. Phleurn olpinum) appear in isolated positions on high mountains in the intervening tropics. No tribe is confined to one hemisphere and no large genus to any one floral region; facts which indicate that the separation of the tribes goes back to very ancient times. The revision of the Australian species by Bentham well exhibits the wide range of the genera of the order in a flora generally so peculiar and restricted as that of Australia. Thus of the Q0 indigenous genera (many monotypic or very small) only 14 are endemic, 1 extends to South Africa, 3 are common to Australia and New Zealand, 18 extend also into Asia, whilst no fewer than 54 are found in both the Old and New Worlds, 26 being chiefly tropical and 28 chiefly extra-tropical.

Of specially remarkable species Lygeum is found on the sea-sand of the eastern half of the Mediterranean basin, and the minute Coleanthus occurs in threeor four isolated spots in Europe (Norway, Bohemia, Austria, Normandy), in North-east Asia (Amur) and on the Pacific coast of North America (Oregon, Washington). Many remarkable endemic genera occur in tropical America, including Anornochloa of Brazil, and most of the large aquatic species with separated sexes are found in this region. The only genus of flowering plants peculiar to the arctic regions is the beautiful and rare grass Pleuropogon Sabinii, of Melville Island. "

Fossil Grasses.-While numerous remains of grass-like leaves are a proof that grasses were widespread and abundantly developed in past geological ages, especially in the Tertiary period, the fossil remains are in most cases too fragmentary and badly preserved for the determination of genera, and conclusions based thereon in explanation of existing geographical distribution are most unsatisfactory. There is, however, justification for referring some specimens to Arundo, Phragmites, and to the Barnbuseae. V

BIBLIOGRAPHY.-E. Haekel, The True Grasses (translated from Engler and Prantl, Die natiirlichen Pjlanzenfamilien, by F. Lamson Scribner and E. A. Southworth); and Andropogoneoe in de Candolle's Monographiae phanerogarnariim (Paris, 1889); K. S. Kunth, Revision des grarninées (Paris, 1829-1835) and A grostographia (Stuttgart, 1833);]. C. Doll in Martius and Eichler, Flora Braszliensis, ii. Pts. II. and III. (Munich, 1871-1883); A. W. Eichler, Bliithendiagromrne i. 119 (Lei zig, 1875); Bentham and Hooker, Genera plantar urn, iii. 1074 (London, 1883); H. Baillon, Histoire des plantes, xii. 136 (Paris, 1893); J. S. Gamble, “ Barnbuseae of British India " in Annals Royal Botanic Gardens, Calcutta, vii. (1896); John Percival, Agricultural Botany (chapters on “ Grasses, ” 2nd ed., London, 1902). See also accounts of the family in the various great floras, such as Ascherson and Graebner, Synopsisder mittelenropaischen Flora; N. L. Britton and A. Brown, Illustrated Flora of the Northern United States and Canada (New York, 1896); Hooker's Flora of British India; Flora Capensis (edited by W. Thiselton-Dyer); Boissier, Flora oriental is, &c. &c.