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54. Leaves. — There are four parts of the wheat leaf that should be distinguished: (1) the blade, which may vary in length and width, in shape, in smoothness, and in the prominence of its veins; (2) the sheath, which, as in all plants of the family, clasps the stem tightly and is split down the side opposite the blade; varies in growing plant from green to purple; (3) the ligule, a thin, transparent tissue borne at the juncture of the blade and sheath and clasping the culm, varying in length from .07 to .I of an inch (1.7 to 2.5 mm.'); and (4) the leaf auricle, thin projections of tissue, outgrowths from the base of the leaf blade varying in color
-2 and hairiness.
55. Tillering.-Inasmuch as buds form in the axis of the leaves, by covering with earth, both roots and culms (branches) will form at any node upon the culm. Ordinarily, however, branches form only at the lower nodes. The number A wheat leaf, showing 1, blade, 2. of branches which can form from sheath, 3, ligule, and 4, auricle.
(About natural size.) a single culm is necessarily limited, but each branch may produce a limited number of branches and these branches in turn other branches, so that under favorable conditions several dozen culms and consequently spikes may be produced from a single seed. This is known as tillering and is one of nature's methods of giving the plant power to adapt itself to its environment. Under ordinary field conditions only a comparatively few culms form, but : | The Description of Wheat Varieties. By Carl S. Scofield. U. S. Dept. of Agr., Bureau of Plant Ind. Bul. 47, p. 12.
at least fifty-two spikes have been produced from a single seed.
The "stand” of wheat may be materially affected by the amount of tillering, and, therefore, a study of those conditions which will promote tillering is advisable. On the other hand, it is probable that the best yields are not obtained where too much tillering is encouraged through thin seeding.
“In starting from the seed the stem soon begins to branch. The first leaves which are sent up seem to be a temporary set of organs designed to quickly reach above the soil, that the plant may be supplied with green cells in the sunlight. These leaves form what appears to be the primary shoot of the plant, and spring
from the stem near the seed. They are found to be dead in the spring, along with the germ whorl of roots, in case of several varieties of winter wheat. At the same point where these first leaves arise another stem, apparently a rhizome, branches off from the primary stem. This rhizome has an internode quite unlike all the other lower internodes, not even covered by the sheath of a leaf, and extending about half way to the surface of the soil. In case the seed is planted two inches deep this rhizome is about one inch long. At the top of this internode a joint bears a leaf, and a few other joints follow at very short intervals, each having a bud in the axil of its leaf.” 2
56. The Organs of Reproduction.The flower of the wheat plant has three
stamens. The anthers are attached to A stool of wheat. the tapering end of the thread-like filaCulms are from a single seed ments below the middle. As the flower originally at a. One-third natural size.
opens the filaments rapidly elongate,
pushing up and outside of the glumes the anthers which previously were closely packed about the ovulary. The attachment of the filament to the anther is such that the anther suddenly upsets and the pollen falis out of
1 Neb. Bul. 32, p. 91.
8 Note: The word ovulary is here used in its proper sense, instead of the terme ovary which is so often incorrectly used.
the slits which are formed in the upper end of the two compartments. This process takes place apparently in a very short space of time. (49) The ovulary is one-seeded and is surmounted by two feathery stigmas which prior to the opening of the flower are erect and adjacent. As the flower opens the stigmas fall apart to receive the pollen. Pollination being effected, the stigmas soon wither and the ovulary rapidly enlarges. The development of the ovule (seed) from the period of flowering to maturity is very rapid and emphasizes the importance of proper soil and climatic conditions at that time. (49)
57. The True Flower. — The ovulary, stigma and stamens are enclosed within two chaffy parts, the inner of which is called a palea and the outer and lower the flowering glume. These parts collectively constitute the flower of the wheat. The Organs of reproduction awn or beard is borne on the flowering in wheat: a, ovulary ;
b, styles and stigmas; glume and varies greatly in length in differ C, anthers; d, filaments ent varieties or even in the same spike, or of stamens. Upper
left illustration shows may be entirely wanting. In some varieties flower before opening; the awns are deciduous or partly so upon ripening. They vary in color from very
open and protrude anlight yellow to black.
thers. (After Hays.)
upper right illustration shows flower about to
58. The Spikelet.—Two to five flowers are enclosed within two chaffy and still harder parts called empty or outer glumes. This is called collectively a spikelet. There is considerable variation in the number of flowers maturing seed, due to variety and environment. In the varieties of common wheat there are generally three or more flowers in each spikelet, which usually matures two or three grains,—more commonly two. The outer glumes differ from those in rye by being oval rather than awl
shaped. They vary considerably with variety and thereby fur nish means of distinguishing varieties. They may vary in color from light yellow to black, uniformly or in streaks, may be smooth or hairy (sometimes called velvety), may vary in shape and length. The keel varies in width and distinctness and its
tip or beak in length and sharpness. The shoulder, which is that portion of the glume on either side of the keel, and its tip (auricle) vary in width and shape and the notch between the auricle and the keel varies in depth or may be wanting. The apical glumes, i. e., the outer glumes of the apical spikelet, vary from the other outer glumes and should be separately described.
59. The Spike.—These spikelets in the grass family are arranged in two ways, viz., on a more:
or less lengthened branch or rachilla, as in the
side oat, when the whole head is called a panicle ; view of spike or joined directly to the stem (i, e., by a very let, showing mode of ato
short rachilla), as in wheat, rye and barley, tachment to when the head is called a spike. (51) In wheat,
rye and barley, as in several other species of the grass family, the spikelets are arranged alternately at the joints of the zigzag jointed stem or rachis, the stem being excavated on the side next the spikelet. In the wheat genus (Triticum L.) there is but one spikelet at each joint and it is placed flatwise, usually on a single spike. There is usually borne on the rachis at the base of each spikelet a growth of short bristly hairs, to which Scofield has given the name of basal hairs. These may be either white or brown in color and may vary in length or be wanting. Often in the cultivated varieties and always in the wild species, the lower one to four spikelets are sterile. The empty glumes are somewhat broader than the flowering glumes. The number of spikelets in a spike
Front and side
IU S. Dept. of Agr., Bureau of Plant Ind. Bul. 47, p. 14.
varies widely with the variety, soil, climate and culture. In this country a good spike of wheat will usually contain from fifteen to twenty fertile spikelets and contain from thirty to fifty grains. There is a marked difference between the length of the spikes of English and American grown wheats. In the United States the length of the spike varies from three to four and a half inches, a common length being three and threefourths inches. Hallet has reported raising a spike of wheat eight and three-fourths inches long and containing 123 grains produced by five years of selection and favorable environment from a spike four and three-eighths inches long and containing forty-seven grains. Investigations by Lyon seem to show no relation between average weight of grain and the number on the spike.
The yield of wheat is affected by four factors, viz., (1) the number of spikes per a given area, (2) the number of spikelets in a given spike, (3) the number of grains in a spikelet, and (4) the weight of the grain. While there is no probability that such results as were reported by Hallet can be obtained in this country, it seems that the most hopeful method of increasing the yield is by increasing the number of spikelets in a spike.
The spike varies in compactness and in form. When viewed sidewise it may be straight or curved; may taper toward apex, both ways or have uniform sides, or may be clubbed at the upper end. The tip may be acute on account of undeveloped spikelets or blunt because they are well filled. The base of the spike may be tapering or abrupt for similar reasons. When viewed endwise the spike may be square, Aattened with spikelets or flattened across spikelets.
60. The Grain.—The wheat grain is a unilocular, dry, indehiscent fruit called a caryopsis, with a thin membranous pericarp adnate to the seed, so that pod and seed are incorporated in one body. The grain is longer than broad, hairy at the apex, slightly compressed laterally, has a deep furrow on