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no more than one
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 one
fourteenth of the DO O $0.0*0 0
61. The Embryo. 0 0 0 @ @
-The embryo can Progressive sections of grain of wheat taken at the three
be divided into (1) axes as indicated, showing shape of grain and position scutellum, or absorband ratio of (x) embryo to (y) endosperm. (From microphotographs by Rowlee.)
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.
I Neb. Bul. 32, p. 103.
62. The Endosperm. Under the microscope the endosperm is geen 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. 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.? 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. 3 Compt. Rend. Acad. Sci., Paris, 126 (1898), No. 22, pp. 1592-1995.
unripe grain within two layers of cells, the inner and outer integuments of the ovulary. In the mature grain the inner integument may have been absorbed, leaving only the outer,
known as the testa. The testa is in turn enclosed by the peri. carp, corresponding to the pod in the pea. The pericarp is composed of three rows of cells and con
stitutes a rather larger Cross section of grain of wheat on the left. (From micro
portion of the grain photograph by Tolman.) Transverse section, on the than do the testa and right, of an unripe grain enlarged about 100 times
nucellus together. from drawing by Bessey. 1. ovary wall or pericarp ; 2, outer integument; 3, inner integument; 4, remains These envelopes are of nucellus; 5, aleurone cells; 6, starch cells.
sometimes spoken of collectively as the bran. Bessey ? and Snyder? give different portions of the wheat grain as follows:
· · 3-4
Girard gives the per cent of embryo in four varieties of wheat as 1.50, 1.41, 1.35 and 1.16 respectively.:
Since the mill products of wheat average considerably less than nine per cent crude fiber, and since seventy per cent of a wheat grain is converted into flour, it follows that the seed coats of the wheat grain must either be considerably less than
1 Neb. Bul. 32, p. III.
five per cent or the seed coats must be largely composed of something else than crude fiber.
65. Physical Properties. Richardson found as the result of 377 determinations that there were about 12,000 grains in a pound of wheat: in some samples there were less than 8,000, while in others 24,000 grains to the pound. Obviously, so far as individual grains are concerned, one bushel of seed in the one case would be equivalent to three bushels in the other. Pammel and Stewart report variations in the specific gravity of American grown varieties from 1.146 to 1.518.
The hardness of the grain varies greatly. Generally the harder grains contain the higher per cent of total nitrogen and of gluten. The relation between hardness and specific gravity has not as yet been clearly demonstrated, although Lyon has shown that high specific gravity is associated with low nitrogen content.
Kornicke and Wernera state that the specific gravities of the various chemical constituents of the wheat grain are as follows: Starch, 1.53; sugar, 1.60; cellulose, 1.53; fats, 0.91-0.96; gluten, 1.30; ash, 2.50; water, 1.00; air, .001293.
The standard (and generally legal) weight per bushel (2150.42 cu, in.) of wheat is sixty pounds. The weight of a measured bushel not infrequently varies from fifty-five to sixty-five pounds per bushel, and greater extremes have been noted.
The color of the grain varies from a very light yellow through varying grades of amber to dark red. Hardness of grain and high nitrogen content are usually associated with the deeper red color.
The grain may vary in length, in transverse or cross section outline, or in depth of crease or furrow. All of these characters may be used in describing varieties of wheat. (201)
1 A Method for Improving the Quality of Wheat for Breadmaking. Thesis for degree Ph.D., Cornell, 1904.
8 Handbuch des Getreidebaues Bd. 28. 120. Berlin, 1884
II. COMPOSITION. 66. Composition.—The following table gives the minimum, maximum and average analyses of 310 American grown samples of grain and seven samples of wheat straw:1
07. Water.—The analyses show that wheat contains ten to eleven per cent of water. This represents the moisture in the samples as analyzed, often after they have stood in the dry room of the laboratories. What percentage of water wheat contains as it goes on the market cannot be stated, but it has been shown to vary largely from day to day with varying cor.ditions of the atmosphere. In California, where the atmosphere inland is very dry at harvest, this subject is a matter of considerable commercial importance. It is claimed that the moisture that this California wheat will absorb during a voyage from San Francisco to Liverpool will sometimes increase its weight enough to pay the entire cost of freight. Wheat bought inland and kept in warehouses all the season would increase in a similar manner upon exposure.
Experiments by Hilgard and O'Neil, of the University of California, indicated that wheat of the inland of California might increase twenty-five per cent in weight by the absorption of water when transported to a temperate climate, while a gain of five to fifteen per cent mignt be looked for with absolute certainty. A difference of nine per cent was observed in twenty-four hours. Brewer found a difference of from five to
1 U. S. Dept. of Agr., Office of Exp. Stations E. S. B. 11.