Part 26

Order 3. =Gramineæ= (=Grasses=). The stems are cylindrical, generally _hollow_ with _swollen nodes_, that is, a swelling is found at the base of each leaf which apparently belongs to the stem, but in reality it is the swollen base of the leaf. The leaves are _exactly alternate_; the sheath is _split_ (excep. _Bromus_-species, _Poa pratensis_, _P. trivialis_, _Melica_, _Dactylis_, etc., in which the sheath is not split), and the edges overlap alternately, the right over the left, and _vice versâ_; the _ligule_ is nearly always well developed. In general, the flowers are hermaphrodite; they are borne in _spikelets_ with _alternate floral-leaves_, and the spikelets themselves are borne in either _spikes_ or _panicles_. The two (seldom more) _lowest floral-leaves_ in each spikelet (Fig. 289 _øY_, _nY_) are _barren_ (as the covering-leaves in many umbels and capitula); these are termed the _glumes_. The succeeding floral-leaves, each of which supports one flower as its bract, are called the _outer pales_ (_nI_); these sometimes each bear an “awn” (a bristle-like body which projects in the median line either from the apex or the back); sometimes the upper ones are barren. Each flower has a _bracteole_, which is placed on the inside opposite the main axis; it is thin, _binerved_ or _two-keeled_, and never has an awn; it is known as the _inner pale_ (_øI_). Immediately succeeding the bracteole are: (_a_) some _small, delicate scales_ (_lodicules_, Figs. 287 _D_, 288 _C_, 290 _L_); (_b_) _three stamens_ with anthers _versatile_, so as to be easily moved, and usually notched at each end (Fig. 287 _C_); and (_c_) a simple gynœceum formed of _one carpel_ with _two styles_ having generally _spirally-branched stigmas_ (Figs. 287 _D_, 288 _C_). The ovary is _unilocular_, and contains one ascending or pendulous, anatropous ovule. _Fruit a nut_, whose seed is always _firmly united with the thin pericarp_ (“caryopsis”). The embryo is larger than in the Cyperaceæ and is placed at the base of the seed, but on the _outer convex surface_ of the pericarp (Figs. 287 _I_, 288 288 _D_, 291), _outside the endosperm_; plumule large with several leaf-primordia. On germination the cotyledon remains in the seed.

The majority of Grasses are annual or perennial herbs; tree-like forms being only found in the Tropics, for example, the Bamboos; they branch (in tufts), especially from the axils of the basal-leaves, while those which are borne higher on the stem are separated by longer internodes and have no vegetative branches in their axils, though a few forms, like _Bambusa_ and _Calamagrostis lanceolata_, produce branches in these axils.

Only a few Grasses have a _solid stem_, such as Maize, Sugar-cane, and _Andropogon_. The _blade_ is flat in the meadow-grasses, but the Grasses which live on dry places (“prairie-grass”) exposed to the sun, often have the blade tightly rolled up and almost filiform or bristle-like, with anomalous anatomical structure. A _closed_ tubular _sheath_ is found in _Melica uniflora_, _Bromus_-species, _Poa pratensis_ and _trivialis_, _Briza_ and some _Glyceria_-species. The sheath is developed for the purpose of supporting the young internodes while their growth is proceeding at the base. The “nodes” (the swollen joints which are seen on stems of Grasses) are not really part of the stem but are formed by the base of the leaf-sheath. They play a part in assisting the haulms to regain a vertical position when laid prostrate by wind or rain. The _awn_ on the pale is homologous with the blade of the Grass-leaf, and the pale itself is the sheath. The arrangement of the leaves in the _spikelet_ is similar to that in _Cyperus_ and other Cyperaceæ, their floral-leaves being borne in several rows in _Streptochæta_. More than two barren “glumes” are found in _Streptochæta_, several Phalarideæ and others. The spikelets, too, are again arranged in two rows in the axils of suppressed floral-leaves. The inflorescence becomes a “compound spike” (ear) when the spikelets are sessile. In the majority of instances the spikelets are borne on long stalks; when these branch, then the secondary branches, and similarly all branches of higher order, are placed so far down upon the mother-axis that they all appear to be of equal value and to arise in a semicircle from the mother-axis itself, though in reality they arise from each other (_Panicle_, Fig. 288 _A_). Sometimes the main axis and branches of different orders unite together as in _Alopecurus_, _Phleum_, and some other Grasses, and hence the single (short-stalked) spikelets appear to arise singly and spirally, or without any definite order, directly from the main axis, with the production of a _cylindrical_ inflorescence bearing “spikes” _on all sides_, that is, a “_spike-like panicle_.”--Many inflorescences are somewhat dorsiventral. The _flower_ is rarely unisexual (_Zea mais_) or barren. Considerable difficulty is experienced in reducing the Grass-flower to the ordinary 3-merous Monocotyledonous type. Some authorities consider the _lodicules_, which are present in all Grasses but absent in the Cyperaceæ, to be homologous with a perianth. According to a more recent theory they are bracteoles, and hence the Gramineæ, like many of the Juncaceæ, have 2–3 bracteoles placed in two rows in the median plane. If this theory be correct, the _flower is naked_. The lodicules expand quickly and cause the opening of the flower (_i.e._ the two pales become separated from each other). Generally only 3 _stamens_ belonging to the outer whorl are present (Fig. 290), as in _Iris_ (Fig. 279), certain Juncaceæ and Cyperaceæ (Fig. 284), but in some, such as the Rice and certain species of Bamboos, all 6 are found. _Pariana_ has more than 6. Only 1 of the _carpels_ is present, namely, the anterior (of those in Fig. 284), so that the ventral suture and the place of attachment of the ovule are situated at the back of the ovary. The number of styles does not correspond with the number of carpels, and the styles may therefore be supposed to arise from the edges of the leaf to the right and left--a position which is not without analogy. In addition, a stylar projection is sometimes found on the anterior side and in the median line (_e.g._ in _Phragmites_), and the solitary style in _Nardus_ has exactly this position; a similar arrangement is found in some species of _Bambusa_ which have only one style; other species of _Bambusa_ have three styles. A tripartite style is found in _Pharus_.

[The Grass-flower may be reduced to the ordinary Monocotyledonous type thus:--The outer pale is the bract of the flower since it bears in its axil the floral shoot; the inner pale occupies the customary position of the bracteole. The fact that it is binerved can be explained by its having been pressed against the main-axis during development. Similar binerved bracteoles are found in _Iris_ (Fig. 279). These bracteoles in both Grass and Iris arise from single primordia, and are not produced by the coalescence of two leaves. The lodicules are the only parts of the perianth remaining, the outer whorl having been suppressed, and also the posterior leaf of the inner whorl; a posterior lodicule, however, is found in the Rice and some species of Bamboo. The outer whorl of stamens is usually absent, though this again is present in the Rice and Bamboo. The three carpels are reduced to one with two or sometimes three stigmas.]

THE FLOWERING. In the panicles the flowers open in basipetal order; the flowers in the spikes situated somewhat above the middle, commence to open first, and the flowering proceeds upwards and downwards. A few Grass-flowers never open (cleistogamic); _Leersia oryzoides_, _Stipa_-species, and _e.g._ Wheat and Rye in cold damp weather; some open their pales so wide that the anthers and stigmas may protrude at the top; most frequently the lodicules expand and force the pales suddenly and widely apart. The filaments elongate considerably, so that the anthers are pendulous and the stigmas unfold. In some Grasses _e.g._ Wheat, the blooming of each flower only lasts a short time. POLLINATION is generally effected by the wind. The _Rye_ separates the pales very widely in the morning, and allows the anthers and stigmas to appear; it is almost entirely sterile when self-pollinated. The _Wheat_ flowers at any time of the day, each flower lasting only a quarter of an hour. The pales open suddenly, but only half way, and the anthers scatter one-third of the pollen in their own flower and two-thirds outside. Self-pollination is effectual, but crossing gives better results. In _Hordeum vulgare_ (all flowers ☿) the flowers of the 4 outer rows behave as in the Wheat, but those in the two central rows always remain closed. The ☿-flowers in the two central rows of _H. distichum_ remain closed and fertilise themselves; they open exceptionally, and may be pollinated by the ♂-flowers in the 4 lateral rows. _H. hexastichum_ is cleistogamic. _Oats_ pollinate themselves.

_The ripe Grass-fruit_, in some species of Bamboo, is a berry; in some other Grasses a nut with _loosely_ lying seed, in some even a capsule, but otherwise a “caryopsis.” In some instances it is loosely enveloped by the pales (Oat), in others firmly attached to these (Barley), and finally, in others, “naked,” _i.e._ it is entirely free from the pales (Wheat and Rye). On the ventral side there is a groove (Fig. 288 _E_); on the anterior side (dorsal suture), which is turned towards the inner pale, it is convex, and at the base on this side, inside the testa, lies the embryo (Fig. 288 _D_). The apex of the fruit is often hairy (Fig. 293). The _skin_ (Fig. 291, _a_) is formed by the pericarp and testa, and in some cases (Barley) the pales also form the outer portion. The endosperm (_b_) is large, and formed of parenchymatous, starch-containing cells: aleurone (proteid) grains may also be found among them. When the starch-grains and the aleurone-grains adhere together the endosperm becomes “horny,” but is “floury” when the starch-grains lie loosely with air between them. In the most external region, just beneath the skin, 1–several layers of nearly cubical cells (filled principally with aleurone-grains and fat) are found, the _aleurone_-layer (Fig. 292). The embryo (Fig. 291 _c-d_) contains large quantities of fatty oil; the large shield-like structure, attached to the embryo and turned inwards towards the endosperm (_c_), is the cotyledon (scutellum); it remains enclosed in the seed during germination, and dissolves the endosperm by means of the peculiar epithelial cells developed on the dorsal surface. The radicle, on germination, is obliged to perforate a mass of cells derived from the suspensor and which form the “root-sheath” (coleorhiza, Fig. 293) round its base. In addition to the tap-root, lateral roots are frequently developed before germination; these quickly break through, and later on are followed by others which appear at the base of the leaf (Figs. 293, 294).

The DISTRIBUTION OF THE FRUIT is most frequently effected by the wind. The spirally-twisted and hygroscopic awn which persists on the fruits of some species (_Avena_, _Stipa_, etc.) assists in their dissemination, and even helps to bury them in the ground.

The two preceding orders are more closely related to each other than they are to the Gramineæ.

The generic differences are chiefly founded on the form of the inflorescence, the number and sex of the flowers in the spikelets, the shape and relative length of the pales, awns, etc. In addition to these the structure of the fruit and seed presents a great many differences; some have compound starch-grains, while in others they are single; some have 1 layer of aleurone-cells, others have several (Fig. 292), etc.

=1.= BAMBUSEÆ. Tall Grasses with woody, very siliceous stems which bear many branches in the axils of the leaves. 6 stamens. _Bambusa_ (Bamboo).

=2.= ORYZEÆ. _Oryza sativa_ (Rice) is a herbaceous marsh-plant, with panicle and small, 1-flowered spikelets, with two small glumes and two large, boat-shaped, strongly siliceous pales. 6 stamens.--_Leersia._ _Lygeum. Pharus. Zizania aquatica._

=3.= MAYDEÆ. _Zea mais_ (Indian-corn, Maize); the spikelets are unisexual; the ♂-spikelets in a terminal panicle; the ♀-spikelets closely crowded and arranged in many rows in a thick, axillary spike, enclosed by large sheathing-leaves. The ♀-spikelets are 1-(2-) flowered; the ovary bears one, long, filamentous style, with bifid stigma.--_Euchlæna_; _Coix_.

=4.= ANDROPOGONEÆ. _Saccharum_ (Sugar-cane); the spikelets are exceptionally small, 1-flowered, and borne in pairs in many-flowered, long-haired panicles. Tall grasses with solid, sappy stem.--_Andropogon._

=5.= FESTUCEÆ. Grasses with panicle (or spike-like panicle) and 2–several-flowered spikelets. Glumes small, in each case shorter than the spikelet.--_Festuca_ (Fescue) and _Bromus_ (Brome, Fig. 288) have the awn placed at the _apex_ of the pale, or slightly below it. _Festuca_ has perennial species, with only a sparsely-branched panicle with branches solitary or in pairs, and round spikelets; the leaf-sheath is widely open. _Bromus_ has the branches borne in half whorls, and the leaf-sheath scarcely half open. _Brachypodium_ has very short-stalked spikelets in a raceme.--_Poa_ (Meadow-grass), _Briza_ (Quaking-grass) and _Glyceria_ have awnless spikelets; these in _Poa_ are ovoid, compressed, and with sharply-keeled glumes; in _Briza_ they are broad, cordate and drooping, with boat-shaped glumes; in _Glyceria_ round, long, many-flowered, linear or lanceolate; some species of _Glyceria_ have closed leaf-sheaths.--_Dactylis_ (Cock’s-foot) differs from all others in the somewhat crowded and unilateral (subsecund) spikelets, which are compressed and oblique (_i.e._ one side more convex than the other).--_Phragmites_ (_P. communis_, Reed); the lowermost flowers of the spikelet are ♂; its axis is covered with long, silky hairs; pales without awns, but acuminate. Perennial marsh-plants.--_Melica_; panicle small, sparsely-branched with round, awnless, few-flowered, usually drooping spikelets. The upper pales, with arrested flowers, are generally united into a club-like mass.--_Molinia_, _Eragrostis_, _Koeleria_, _Catabrosa_.--_Cynosurus_ (Dog’s-tail) has a small, spicate panicle with unilateral spikelets, some of which are fertile, some barren, each supported by a pectinate scale. _Arundo. Sesleria. Gynerium. Triodia._

=6.= AVENEÆ. Panicles with 2–many-flowered spikelets; at least one of the glumes is quite as long as the entire spikelet.--_Avena_ (Oat). The pale is boat-shaped, often bifid, and at about the middle of the back has a twisted, bent awn.--_Aira_ (Hair-grass) has a long-branched panicle with small, 2-flowered spikelets; the pale has a dentate apex and bears an awn on the posterior side close to the base.--_Weingærtneria._--_Holcus_ (Yorkshire-fog); a soft, hairy Grass with an open panicle, keeled glumes; 2 flowers in the spikelet, of which the lower one is ☿, the upper ♂; the pale which supports the ☿-flower has no awn, but that which supports the ♂-flower, on the contrary, is awned.

=7.= AGROSTIDEÆ. Panicles or spike-like panicles with 1-flowered spikelets. Generally 2 glumes and only 1 pale.--The following have PANICLES: _Milium_ with square panicle-branches and round spikelets; _Agrostis_ (Fiorin), with compressed, glabrous spikelets, whose glumes are longer than the pales. _Calamagrostis_ differs in having a chaplet of long hairs at the base of the pale.--_Stipa_ (Feather-grass) has a long, twisted awn.--The following have SPIKELIKE PANICLES: _Phleum_ (Cat’s-tail, Timothy-grass) has sharply pointed, entirely free glumes, which are much longer than the awnless pales. _Alopecurus_ (Fox-tail); glumes united below; pale with awn. _Ammophila_ (_Psamma_). _A. arundinacea_; pales hairy at base; perennial, stiff-leaved, glaucous sand-grass with creeping rhizome. _Aristida. Sporobolus._

=8.= PHALARIDEÆ. Panicles and spike-like panicles. The spikelet has in the upper part a single fertile flower; below it are placed 4 pales, of which the upper 1–2 sometimes support ♂-flowers. On the whole, 6 floral-leaves of the first order are present.--_Phalaris_ (_P. canariensis_, Canary-grass) has an ovate, spike-like panicle, the spikelets are compressed, convex on the outer side, concave on the inner. The large glumes are winged on the back.--_Digraphis_ (_D. arundinacea_) is closely allied to _Phalaris_, but the keel of the glumes is not winged.--_Anthoxanthum_ (_A. odoratum_, Sweet-vernal) has a small, lanceolate, open, spike-like panicle; the spikelets have below 2 barren flowers, and above these an ☿-flower with 2 stamens. The upper glume is longer than the flower.--_Hierochloa._

=9.= CHLORIDEÆ. The spikelets are arranged in the form of a spike in two rows on one side of an often flatly-compressed axis; they are mostly 1-flowered.--_Chloris_; _Ctenium_; _Cynodon_; _Eleusine_; _Microchloa_.

=10.= PANICEÆ. The spikelets are borne in panicles or spikes, which may be arranged like fingers or in a raceme. There is a centrally-placed ☿-flower; below it is sometimes a ♂-flower.--_Panicum_; _Paspalum_; _Oplismenus_; _Setaria_ has an almost cylindrical spike-like panicle with several barren branchlets, which project as stiff, rough bristles.--_Cenchrus_; _Pennisetum_.

=11.= HORDEÆ. Spikes compound; spikelets sessile in the notches of a toothed axis.

=A.= Spikelets solitary.--_Triticum_ (Wheat, Fig. 287) has in each tooth of the main axis, a several-flowered spikelet which turns its _flat side_ towards the central axis. The cultivated species (true Wheat) are 1-2-annual, the wild ones (_T. repens_, Couch, also as an independent genus, _Agropyrum_) are perennial, with creeping rhizome and lanceolate glumes.--_Lolium_ (Rye-grass) has in each tooth of the main axis a many-flowered, compressed spikelet, which is placed _edgewise_ towards it and (with the exception of _L. perenne_) has only one outwardly-turned glume (_L. temulentum_ has a rudiment of the inwardly-turned lower glume); the terminal spikelet has two glumes.--_Secale_ (Rye). A two-flowered spikelet in each tooth; small, lanceolate, acuminate glumes. _Nardus_ and _Lepturus_ have very narrow spikes, the former with unilateral spikelets.

=B.= In each notch of the axis 2 or more spikelets are placed close together.--_Hordeum_ (Barley). In each tooth three 1-flowered spikelets. _H. hexastichum_ (6-rowed Barley), has 6 rows of fruits, since all the spikelets are fertile, and _H. distichum_ (2-rowed Barley) 2 rows, since the lateral spikelets are (♂, and barren (p. 292).--_Elymus_ has 2–6 many-flowered spikelets in each joint of the main axis. _Ægilops_ has awns upon the glumes.

DISTRIBUTION. 315 genera with 3,500 species. The order is distributed over the whole world, and as regards number of individuals is perhaps the richest. In the Tropics, large, broad-leaved, tree-like forms are found (_Bambuseæ_, _Olyreæ_, _Andropogoneæ_, etc.; in S. Europe, _Arundo donax_); in England, next to the Compositæ, it is the order most rich in species (about 134).--The origin of some of the cultivated Grasses is lost in obscurity. The Maize, no doubt, was indigenous to America, where its nearest relatives are found, and where it has also been discovered in ancient Indian graves; Durra or Guinea-corn, Millet and Sugar-cane are South Asiatic plants, and our own cereals no doubt have sprung primarily from Western Asia and South-Eastern Europe (Barley from Armenia and Persia, where a very closely related wild species is found; Wheat from the same districts; Rye from the perennial species _S. montanum_). _Panicum altissimum_ and Rice have come from Africa.

USES. The Grasses play a very important part as cereals and fodder plants. The following are the most important of the cultivated ones: _Triticum vulgare_ (common Wheat), _turgidum_, _amyleum_, _polonicum_, _spelta_, _durum_, etc.; _Secale cereale_ (Rye); Barley (_Hordeum_-species, see under the genus); Maize; Oats (_Avena sativa_, _orientalis_, _nuda_); Millet (_Panicum miliaceum_); Durra (Turkish Millet, or Guinea-corn, _Sorghum vulgare_, _cernuum_ and _saccharatum_); Manna-grass (_Glyceria fluitans_). As fodder-plants especially: Rye-grass (_Lolium perenne_); Oat-grass (_Avena elatior_); Timothy (_Phleum pratense_); Fox-tail (_Alopecurus pratensis_); Cock’s foot (_Dactylis glomerata_); Dog’s tail (_Cynosurus cristatus_); Sweet-vernal (_Anthoxanthum odoratum_); Soft grass, or Yorkshire-fog (_Holcus lanatus_ and _mollis_); Quaking-grass (_Briza media_); species of Meadow-grass (_Poa_); Fescue (_Festuca_) and Brome (_Bromus_).--Several cultivated species of Grass are also used in the preparation of _fermented liquors_, the starch in the seeds being transformed to _sugar_ (beer from “Malt,” _i.e._ the germinated Barley; arrack from Rice); or the stem becomes specially saccharine before flowering: the Sugar-cane, _Sorghum saccharatum_.

OFFICINAL. The rhizome of _Triticum repens_, Oat-grain, flour of Barley, and the starch of Wheat, also sugar.

The seeds of _Lolium temulentum_ are considered _poisonous_.--The stems of many species (including our common grains) are used in the manufacture of paper, especially “Esparto grass” (_Stipa tenacissima_) from Spain and N. Africa, and the sheathing-leaves of the ♀-spike of _Maize_. Sand Lyme-grass (_Elymus arenarius_), and especially _Psamma arenaria_, are important.--But few Grass-species are _sweet-scented_: _Anthoxanthum odoratum_ and _Hierochloa odorata_ contain coumarin; _Andropogon_-species have essential oils (“Citronella oil”).--ORNAMENTAL PLANTS are: the “Ribbon-grass” (a variety of _Digraphis arundinacea_), _Stipa pennata_ (whose awn is exceedingly long and feathery), _Gynerium argenteum_ (Pampas-grass), _Lagurus ovatus_, _Hordeum jubatum_, _Bromus briziformis_.

Family 3. =Spadicifloræ.=