Part 15. Characteristics Of Cerials

15. Characteristics of cereals. The general appearance of the most important grain-plants is shown in Figs. 1 to 15. As will be seen, they all agree in having narrow grass-like leaves, and slender upright stems bearing numerous flowers in "ears" or "heads," and finally, kernels enclosed by "chaff" or "husks." In all but maize each separate kernel is covered completely by two or more of these chaffy envelopes, and even in maize some thin papery chaff may be seen attached to the cob at the base of each kernel. All the cereals are annuals; that is to say, each completes its span of life within a year. All of those mentioned, except buckwheat, are grasses which have been more or less changed from their wild state by ages of cultivation.

Let us look more closely at the flowers of the oat. Although appearing rather unlike what we ordinarily call flowers, they have, as will be seen from Figs. 2 and 3, all the parts essential to a true flower. Indeed, because of their simplicity and perfection they afford a convenient standard with which to compare other flowers. In the center of the oat flower, as of flowers in general, is a pistil, in which may be distinguished (1) a lower swollen part, the ovary, containing a small egg-shaped body, the ovule; (2) a pair of elongated middle parts, the styles, each connecting the ovary with (3) a free, terminal part, the stigma, which is here like a little plume. Around the pistil are three stamens very like what are commonly met with in other flowers. Each stamen consists of (1) a double sac, the anther, in which are produced innumerable dust-like particles, the pollen, and (2) a threadlike part, the filament, on the upper end of which the anther is borne. When the anther is ripe it sheds its pollen, a particle of which coming to rest upon an oat stigma brings about the ripening of the ovule into a seed. As the ovule ripens, the ovary enlarges to keep pace with it, forming at last for the seed a firm protective covering which together with the seed constitutes the grain. Meanwhile the styles, stigmas, and stamens, having fulfilled their office, wither and fall off. The ripened ovary and its contents together with whatever parts ripen in connection with it (in this case two husks) constitute the fruit.

Fig. 1.:-The oat (Avena sativa, Grass Family, Gramineoe). Plant in flower, showing several leafy stalks growing from one root. Three of the stalks bear flower-clusters. About one-fifth natural size. (Baillon.)

Since the purpose of the flower is to form seeds, and this is accomplished by means of stamens and pistils, these are called the essential organs of a flower. A flower which has both is said to be perfect; if either alone, imperfect; or if with neither, rudimentary.

Fig. 2.-Oat. A, Upper part of flower-cluster. B, a single spikelet in flower, with bracts spread somewhat apart. C, one of the outer bracts. D, an inner bract bearing an awn. J, pistil. G, lodicules. A and B about natural size, C, D, and J, enlarged. (Nees.)

While the floral parts of the oat are being formed they are protected by papery husks called bracts, a bract being ordinarily a small leaf-like organ belonging to a flower-cluster. A little cluster of grass-flowers together with their bracts, is called a spikelet. At the base of the inner bracts are the so-called lodicules which by swelling spread apart the bracts so as to expose the anthers and stigmas at the proper time for shedding or receiving the pollen. An awn is a bristlelike appendage such as make up the "beard" of many grasses.

Fig. 3.-Oat. A spikelet (similar to B, Fig. 2) cut lengthwise to show the inner parts. Enlarged and somewhat diagrammatic. Sk, stalklet; R, R', its continuation as a little rachis within the spikelet; C, C', outer bracts; M, F, mature flower; Y, F, young flower not yet opened; R, F, rudimentary flower or pair of bracts with neither stamens nor pistils within; D, bract with awn (B); E, inner bract; G, lodicule; F, F', filaments bearing ripe anthers (RA, RA') from one of which pollen (P) is falling; Sg, stigma; Sy, style; Ov, ovary, containing an ovule (Ol); YA, a young anther; YA', a similar one cut lengthwise to show the pollen forming within. (Original.)

Fig. 4.-Oat spikelet in fruit. F, the awned inner bract swollen with the ripe kernel which it enwraps; A, awn; F', another ripe "oat" separated from the little rachis (R) and turned to show its inner face where the edges of the bract enclosing the kernel are seen not quite meeting at the center. About twice natural size. (Original.)

A continuation of the stalk into a flower-cluster is called its rachis.

Every one should be able to tell at sight such important plants as the six principal cereals. When in flower they may be distinguished by the peculiarities mentioned in the following synopsis taken in connection with the figures.

Fig. 5-Rice (Oryza sativa, Grass Family, Gramineoe). P, upper part of rice plant, one-quarter natural size; S a spikelet from the same; L, rain-guard or ligule at base of leaf-blade, inner view; natural size. (Martius.)