CORX STEVCTURE 93 



grain, under the depression or groove, which faces the tip 

 of the ear. It comprises about one eighth of the weight of 

 the grain. It is especially rich in fat. 



The endosperm (from endon, around, and sperma, a seed) 

 is that large portion of the seed lying around and between 

 the embryo and the several outer layers or coats of the ker- 

 nel. The endosperm constitutes about 73 per cent of the 

 weight of the entire grain and is that part of the grain 

 which gives to corn its value as a starchy food. The endo- 

 sperm consists chiefly of starch, but contains also some 

 protein, ash, and other materials. 



This starch of the endosperm is arranged in two different 

 ways, gi\'ing two very different appearances to the different 

 parts of the same endosperm. When this starch is looselj' 

 arranged, the color of that part is a pure snow-white, of an 

 opaque floury appearance. On the other hand, when it is 

 arranged in compact form, the appearance is that of a horny 

 or nearly translucent substance, which is called the horny, 

 or corneous layer. 



The coats of the kernel, which are usually together re- 

 moved in the form of bran, are several in number, each 

 ha\'ing separate function and origin. 



94. Judging the composition of the kernel by its cross- 

 section. — The investigations of Hopkins and of Willard 

 have shown that by cutting transversely through a grain 

 of corn, one may judge of its probable richness in fat, in 

 starch, or in protein, by the thickness of the several layers 

 constituting the germ, the loose floury starch, and the 

 compact horny starch (Fig. 39). A large germ indicates 

 a high percentage of fat, which is important when the corn 

 is used for the manufacture of corn oil. A thick layer of the 



