Fatua, glumes hairy and long and one terminal, rudimentary.
Each spikelet contains a solitary flower with two outer small barren glumes, above which is a large tough, compressed, often awned, flowering glume, which partly encloses the somewhat similar pale.
5 is a spikelet of the female inflorescence, consisting of two outer glumes, the lower one ciliated, which enclose two florets - one (a) barren (sometimes fertile), consisting of a flowering glume and pale only, and the other (b) fertile, containing the pistil with elongated style.
B, Barren glumes; f, flowering glumes.
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.
- Spikelet of Anthoxanthum (enlarged) without the two lower barren glumes, showing the two upper awned barren glumes (g) and the flower.
9), Coleanthus, Nardus) the spikelet consists of nothing more, but usually (even in uniflorous spikelets) other glumes are present.
Of these the two placed distichously opposite each other at the base of the spikelet never bear any flower in thei axils, and are called the empty or barren glumes (figs.
They are the " glumes " f of most writers,.
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, Manisuris, Anthe- phora, Peltophorum), so as to afford greater protection to the flowers or fruit.
Rarely the inflorescence consists of very few flowers; thus Lygeum Spartum, the most anomalous of European grasses, has but two or three large uniflorous spikelets, which are fused together at the base, and have no basal glumes, but are enveloped in a large, hooded, spathe-like bract.
B, ing glume; p, Barren glumes; f, flower pale.
The pair of barren glumes (b) are separated from the flowering glume, which bears a long awn, twisted below the knee and feathery above.
Fertile glumes, each enclosing one flower with its pale d.
Thus the species' of wheat are usually selffertilized, but cross-fertilization is possible since the glumes 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.
One-flowered spikelets may fall as a whole (as in the tribes Paniceae and Andrepogoneae), or the axis is jointed above the barren glumes so that only the flowering glume and pale fall with the fruit.
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 H olcus, 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 spikelets; in others, as in Arundo (a reed-grass), the flowering glumes are enveloped in long hairs.
In Tragus the glumes bear numerous short hooked bristles.
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.
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.
A Fertile glume and pale hyaline; empty glumes thick, membranous to coriaceous or cartilaginous, the lowest the largest.
Li Fertile glume and pale cartilaginous, coriaceous or papery; empty glumes more delicate, usually herbaceous, the lowest usually smallest.
Spikelets oneto 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.
Empty glumes 4.5.
Empty glumes 2.6.
Fertile glumes generally shorter than the empty glumes, usually with a bent awn on the back.
Fertile glumes generally longer than the empty, unawned or with a straight, terminal awn.
The outer glumes are acute and glabrous, the flowering glumes lance-shaped, with a comb-like keel at the back, and the outer or lower one prolonged at the apex into a very long bristly awn.
At the base of each spikelet are two empty boat-shaped glumes or "chaff-scales," one to the right, the other to the left, and then a series of flowers, 2 to 8 in number, closely crowded together; the uppermost are abortive or sterile, - indeed, in some varieties only one or two of the flowers are fertile.
On the other side of the flower and at a slightly higher level is the "palea," of thinner texture than the other glumes, with infolded margins and with two ribs or veins.
These several glumes are closely applied one to the other so as to conceal and protect the ovary, D E FIG.
B, Glumes, from side.
C, Glumes, from back.
The stamens are placed round the base of the ovary, which is rounded or oblong, much smaller than the glumes, covered with down, and surmounted by two short styles, extending into feathery brush-like stigmas.
Polonicum, or Polish wheat, is a very distinct-looking form, with long leafy glumes; its origin is not known.
In the turgid wheats the glumes have long awns, and the seed is turgid and floury, as in the common wheats.
In the hard wheats the outer glumes are keeled, sharply pointed, awned, and the seed is elongated and of hard glassy texture, somewhat translucent, and difficult to FIG.
The Polish wheat, rarely if ever cultivated in the United Kingdom, has very large lanceolate glumes, longer than the spikelet, and elongated glassy seeds.
In the jointed or spelt wheats the distinctions lie in the presence of awns, the direction of the points of the glumes (straight, bent outwards, or turned inwards), the form of the ear as revealed on a cross-section, and the entire or cleft palea.
Under natural circumstances wheat is selffertilized: that is to say, the pollen of any given flower impregnates the stigma and ovule of the same flower; the glumes and coverings of the flower being tightly pressed round the stamens and stigmas in such a way as to prevent the access of insects and to ensure the deposit of the pollen upon the stigmas of the same flower.
The stamens of the wheat plant may frequently be seen protruding beyond the glumes, and their position might lead to the inference that cross-fertilization was the rule; but on closer examination it will be found that the anthers are empty or nearly so, and that they are not protruded till after they have deposited the pollen upon the stigma.
The separation of the glumes, which occurs at the time of fertilization, and which permits the egress of the useless stamens after that operation, occurs only under certain conditions of temperature, when the heat, in fact, is sufficient to cause the lodicules of the flower to become turgid and thus to press apart the glumes.
The glumes have to be separated and the anthers cut away before the pollen is fully formed, care being taken at the same time not to injure the stigma, and specially not to introduce, on the scissors or otherwise, any pollen except that of the variety desired.
- Spikelet of Oat (Avena sativa) laid open, showing the sterile bracts gl, gl, or empty glumes; g, the fertile or floral glume, with a dorsal awn a; p, the pale; fs, an abortive flower.
A, b, Barren glumes; c, fertile glumes, each enclosing one flower with its pale, d; the zigzag axis (rhachilla) bears long silky hairs.
- Flower of a grass with glumes removed, showing three stamens and two feathery styles.