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of grain. It would not appear that there is any necessary relation between the length of straw and the yield of grain, although all other things equal, the longer the culm, the greater the yield of grain. The club varieties of wheat grow about two feet high, while common wheat varieties grow to a height of from three to five feet; probably the average height is four feet.
The length of the culm has an important influence upon the liability to lodge, and also influences the ease of harvesting. It seems probable that the yield of straw may affect the loss in soil fertility, especially if the straw is not returned to the soil. On land of good average fertility the Ohio Station produced ninetyfive pounds of straw for each bushel of wheat during a period of ten years' continuous culture without fertilizers; 115 pounds per bushel where a complete commercial fertilizer was used, and 111 pounds per bushel where farm yard manure was used annually.1
During the early growth of wheat the nodes are very close together and consequently the plant consists principally of leaves. This condition obtains until the wheat begins to shoot, which consists of the lengthening of the internodes and the pushing up of the spike. The leaves which were formerly bunched together within a foot of the surface of the ground are now scattered along the culm, and in field conditions are comparatively scanty, and apparently inactive, except near the top of the culm, even at the time of blossoming. As the weight of the starch, as well as other material laid up in the seed subsequent to this time, is large, and as no starch is found laid up in the leaves prior to this time, as in some other plants, the question has been raised as to the ability of the active leaves to elaborate so much starch in so short a time. In fact, during the latter part of the ripening period only the glumes and the upper part of the stem remain green. Investigations indicate that the glumes do not have the capacity to form carbohydrates from the air, while the upper part of the stem has such power.2
1 Ohio Bui. 110, p. 47.
2 Ann. Agron. 28 (1902), No. 10, pp. 522-527. (E. S. R., Vol. XIV, p. 634.)
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 .1 of an inch (1.7 to 2.5 mm.1); and (4) the leaf auricle, thin projections of tissue, outgrowths from the base of the leaf blade varying in color 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 of branches which can form from 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. Bui. 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 the tapering end of the thread-like filaments below the middle. As the flower opens the filaments rapidly elongate, pushing up and outside of the glumes the anthers which previously were closely packed about the ovulary.8 The attachment of the filament to the anther is such that the anther suddenly upsets and the pollen falls out of
1 Neb. Bui. 32, p. 91.
2 Minn. Bui. 62 (1899), p. 407.
8 Note: The word ovulary is here used in Its proper sense, instead of the term 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 awn or beard is borne on the flowering glume and varies greatly in length in different varieties or even in the same spike, or may be entirely wanting. In some varieties the awns are deciduous or partly so upon ripening. They vary in color from very light yellow to black.
Organs of reproduction in wheat: a, ovulary;b, styles and stigmas;c, anthers ; d, filaments of stamens. Upper left illustration shows flower before opening; upper right illustration shows flower about to open and protrude anthers. (After Hays.)
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 awlshaped. They vary considerably with variety and thereby furnish 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 oat, when the whole head is called a panicle; or joined directly to the stem (i. e., by a very short rachilla), as in wheat, rye and barley, 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.1 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
I U. S. Dept. of Agr., Bureau of Plant Ind. Bui. 47, p. 14.