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.

३:४

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 an thers. (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 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.

Front and side

view of spikelet, showing

mode of attachment rachis.

to

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. 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

1 U. 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, flattened 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

the side opposite the embryo, causing a deep infolding of the pericarp or bran, which makes the roller process of milling a superior method. It is characterized by a small embryo, and a large development of endosperm from which the flour is obtained. Bessey estimates the cubic contents of a wheat

grain to be from twenty to thirty cubic millimeters, of which fully thirteenfourteenths are filled with starch cells, the embryo occupying

no more than onefourteenth of the space.1

61. The Embryo. -The embryo can be divided into (1) scutellum, or absorb

ent organ, which on germination causes

the dissolution of the endosperm and then transfers it to (2) the vegetative portion. This vegetative portion contains in miniature the first leaves and roots of the new plant. The embryo contains a relatively high per cent of ash, protein and fat, and considerable quantities of soluble carbohydrates (sugar), but probably little if any starch. About one-sixth is fat or oil and about one-third is protein, the two thus constituting one-half of the embryo. The proteids of the embryo differ also from those of the endosperm in the ease with which they undergo changes. Osborne has found the embryo to contain about 3.5 per cent of nucleic acid.2

1 Neb. Bul. 32, p. 103.

2 Conn. Rept. 1901, pp. 365-430.

62. The Endosperm.-Under the microscope the endosperm is seen to consist of large elongated thin-walled cells, with their longer axis usually at right angles to the surface of the grain. These cells are filled with starch granules varying in size and form, but when full grown they are rounded or oval in shape and reach a diameter of thirty-seven micromillimeters, or 675 to the inch.1 The composition of the flour shows the presence of ash and proteids, although under the microscope usually starch only can be seen in the mature grain. M. E. Fleurent has separated the endosperm from the rest of the grain and has subdivided it into three portions from the center outward.2 There was a material variation in the per cent of gluten in the endosperm of different varieties and a marked variation in successive portions from center outward, both in the per cent of gluten and the proportion of glutenin to gliadin. (70) Proceeding from center outward, the per cent of gluten varied in a French variety from 7.37 to 9.51, in an Indian variety from 8.03 to 10.24, and in a Russian variety from 10.88 to 13.22. The per cent of flour was largest (73.02 per cent) in the Indian variety and least (67.25 per cent) in the Russian variety.

63. The Aleurone Layer.-The endosperm, along with the embryo, is enclosed in a single row of comparatively large cells rather regular and rectangular in transverse or cross section. When viewed perpendicular to the surface these cells are irregular in form. The cells are filled with a substance similar in composition and physical properties to that found in the embryo, and are referred to as aleurone or gluten cells. The gluten of wheat flour does not come from the aleurone layer but from the endosperm.

64. The Bran.-The aleurone layer is enclosed in the nucellus, which in the mature wheat grain is a single layer of collapsed cells or may be wanting. This is enclosed in the

1 Neb. Bul. 32, p. 109.

Compt. Rend. Acad. Sci., Paris, 126 (1898), No. 22, pp. 192-1595.