245. Classification of Dent Varieties.-Dent varieties may be classified into eighteen groups as follows:

Classification based upon maturity is open to the objection that the maturity is affected by season and climate, that what is an early variety in one locality may become a late variety in another, and vice versa. A classification based upon roughness of ear is difficult because of the almost insensible gradation from extreme smoothness to extreme roughness.

A classification based upon specimen ears alone may be as

follows: grains broader than deep, as deep as broad, and deeper than broad. It may be further subdivided according to evenness of ear: shallow rounding, moderately rounding, or deeply rounding at butt; and still further subdivided in accordance with the shape of ear, number of rows per ear, and color of grains.

246. Soft Maize is that type in which the endosperm is white, the corneous endosperm being entirely absent. The shape and outward appearance of the grain is similar to that of the flint type, but varies in size from not much larger than grains of pop maize to the largest known. The variety Cuzco from Peru has grains fifteen-sixteenths inch deep by eleven-sixteenths inch broad. The color is quite variable. The ears resemble those of the flint type, but are usually shorter, with slightly larger diameter.

This type is widely distributed and apparently was largely grown by the Indians on account of the ease with which it could be crushed. It is not grown for commercial purposes in North America. It is said that in some instances it is grown in place of sweet maize for eating green along the western coast of South America. Most of the varieties experimented with in the United States have either not matured or else have been very late in maturing.

247. Sweet Maize is that type in which the endosperm is translucent and horny in appearance, the starch having been more or less reduced to sugar.

What is probably a variation from this type is described by Sturtevant as starchysweet corn (Zea amyleasaccharata Sturt.). In this type the lower half of the grain is starchy, the upper half horny and translucent; otherwise it is like the ordinary sweet type. Varieties of this type were found in the San Pedro Indian collection, but failed to mature at Geneva, N. Y.1

The grains of sweet maize are usually broadly wedge-shaped, with more or less rounded summit and a characteristically wrinkled surface. While varying largely, a typical grain is one

1 Bul. Torr. Bot. Club, Vol. XXI, No. 8, p. 334.