each stalk, as the nearer we have been able to approach such a variety, the greater has been the yield of grain per acre." 1

No two-eared dent variety has ever been produced which has become extensively grown or widely popular. It has not been shown in what way it is easier for a stalk of maize to elaborate the material for two ears than it would be to produce the same grain in one ear. When harvested by hand, varieties bearing but one ear on a stalk are to be preferred, unless the two or more eared varieties yield an appreciably larger quantity of grain. On the other hand, when fed to cattle without removing from stalk, two smaller ears might be preferred. For silage, the total yield of grain would be the only consideration.

222.

Barren Stalks. A varying percentage of the stalks of the field are barren-do not bear any ears. The percentage of barren stalks on a given soil varies with the thickness of planting and the season. Barrenness does not seem to be a variety characteristic. It seems to be largely the result of environment. If it were an hereditary characteristic the fact that the stalks are barren would tend to eliminate them.

223. The Grain. The maize grain has the same general structure as the wheat grain. (60) While quite variable, it is characterized by its large size as compared with the seed of

any other species of the grass family. The weight of 100 grains may vary from three grams in Miniature pop to 100 grams in Cuzco soft. It is also greatly different in shape from the grain of the other cereals, the furrow on the side opposite the embryo being entirely wanting. In most varieties, the grain is flattened and more or less triangular or oval in shape with its lateral diameter greater than the diameter parallel with the axis of the cob, while some varieties have spheroidal and others conical grains.

Viewed from its broader surface, the grain may be broad above and taper by straight lines to a very narrow base, cuneate wedge-shaped; or may be broad above 1 Miss. Bul. 33 (1895), pp. 75-76.

E. L. Sturtevant: Varieties of Corn. U.S. Dept. of Agr., Office of Expt. Sta. Bul 57, p. &

and taper by curved lines to a narrow base, rounded cuneats; or may be broad above, less broad below, connected by straight lines, truncate-cuneate; or sides of grain may be parallel in the upper portion and thence taper to a more or less broad base, shoe-peg form; or may be nearly or quite as broad at base as at summit, rectangular; or the corner may be rounded both above and below, rounded corners. The summit of the grain may be rounded or flat; may end in a long narrow tip, rostrate; or a short abrupt point, mucronate. On the other hand the summit of the grain may be depressed, dented. The indentation may be round or cup-shaped, dimple dented; or longer than broad, long dimple dented: or the sides may be pinched and parallel, crease dented; or the two sides may be pinched together closely and project upward and forward, pinched dented; or with the last condition there may be a more or less ragged projection from the summit on the side next the embryo, ligulate dented.

As a variety characteristic, depth is much more constant than width of grain, the former being a quite constant character.

224. Shape of Grain Upon Maturity.-Sturtevant states that each of the five types of maize furnishes three well-defined subtypes, with parallel relationship throughout. Thus, subtype A, the grain broader than deep; subtype B, the grain as broad as deep; subtype C, the grain much deeper than broad.

"All my collections concur towards the belief that climatic relations are more evident in these subspecies (subtypes) than in the species (types) themselves. With the possible exception of the dent corns and the starchy-sweet, for which as yet but one locality is known, the climatic range and adaptability seem about the same, but in the subspecies (subtypes) there is diversity, A being for climates of short season, C for long seasons, while B in general is intermediate; although a climate suitable for C can grow A and B."2

In a study of 168 varieties, he classifies types and subtypes as follows:

2 Bul. Torrey Bot. Club, Vol. XXI (1894), No. 8 pp. 320-323.

IX.

MAIZE.

I. STRUCTURE (CONCLUDED).

225. The Embryo.-The scutellum and vegetative portion with its miniature leaves and roots can readily be seen with a low power microscope. (61) The embryo situated on the side toward the tip of the ear, while variable in size, is relatively large, variations of from 7.7 to 15.7 per cent having been reported.' In an average ear, not far from one-eighth of the grain is embryo. (60) The embryo is characterized by high percentage of ash, protein and fat. The following per cents in the water-free substance of the embryo have been reported:

In dent maize the embryo contains about twenty per cent of the protein, seventy-five per cent of the ash and eighty to eightyfour per cent of fat of the whole grain.3

226. The Endosperm.-A section of the endosperm varies from snowy white to translucent in appearance. The difference between the types or subspecies of maize is in part based upon the relative amounts and arrangements of the white and translucent or corneous endosperm. When cross-sections of the

1 Ill. Bul. 55, pp. 234-235.

↑ Ill. Bul. 53, p. 140; 87, p. 83.

s Ill. Bul. 87, pp. 90-91.

A, an enlarged longitudinal section of maize. The internal structure is diagrammatic inas much as about 100 times the number of cells in outline (ten times in diameter) occur in the grain. I and 2 show the pericarp; the testa is not shown in A, but is shown in B 10. The nucellus is wanting. 3, aleurone layer; 4, cells of the endosperm; 5, scutellum; 6, plumule; 7, primary root; 8, its root-sheath; 9, a row of cells similar in appearance to aleurone layer but smaller. B, section more highly magnified; shows pericarp composed of two layers; 1, epicarp; 2, endocarp. (The author.)

maize grain are examined under the microscope, no material difference in structure is noticeable. This has led to the suggestion, not positively proven, that the difference between the white and translucent portions of the endosperm is a difference in density analogous to the difference between snow and ice. The difference is readily noted in pop maize before and after popping.

Hopkins reports finding corneous endosperm to contain two per cent more protein than the white endosperm in a dent variety, and makes this the basis of selecting strains of maize for high protein.1 The question may be raised whether the higher percentage of protein found in the corneous endosperm may not be due to lack of complete separation from the aleurone layer. On the other hand, a somewhat similar condition exists in the endosperm of wheat. (62) Analyses of dent, flint, pop and soft varieties of maize in which there are wide differences in the density of the endosperm do not show material differences in the per cent of protein in the whole grain.

The endosperm occupies about seventy-three per cent of the grain, contains about sixty per cent of the protein, four per cent of the fat, twelve per cent of the ash and about eighty per cent of the carbohydrates, principally starch, of the whole grain.

The endosperm contains six to ten per cent of protein, eightynine to ninety-three per cent of carbohydrates and usually less than half a per cent each of ash and fat. It appears probable that the fat found in the endosperm on analysis may be there through absorption from embryo and aleurone layer, since the per cent of fat in endosperm is found to increase with the age of the grain. In sweet maize the starch has been changed in part to sugar.

227. The Aleurone Layer is relatively larger than in the wheat grain, comprising from eight to fourteen per cent of the

1 Ill. Bul. 87, pp. 83-84.

2 Ill. Bul. 87.