i64 TEXTBOOK OF BOTANY 



the outside ; indeed, it is very difficult to make them out at 

 all in the ripe kernel. 



186. Kinds of Food in the Kernel. — Since the food stored 

 within the kernel is the part of the com plant that is valuable 

 to us, it is worth while to learn something of its nature. The 

 kernel contains four different kinds of substances that will 

 be useful as food either to the young com plant that may 

 grow from the seed, or to the man or the animal that may eat 

 it. These food substances are starch, which is present in 

 the form of minute grains within the endosperm ; sttgars, 

 also in the endosperm as well as to some extent in the 

 embryo ; fats, present in small amounts in the endosperm, 

 but much more largely in the embryo ; and proteins, present 

 in the living matter of the embryo and in that of the endo- 

 sperm as well, and especially in certain rounded bodies in 

 the outermost layer of the endosperm next the seed coat. 

 These four classes of food substances are exactly those of 

 which our diet, as well as that of the lower animals, is chiefly 

 made up, and it is the presence of these substances that makes 

 the kernels of Indian com and other grains so useful to us. 



The food value of com, as of wheat and rye, lies mainly 

 in its starch. The other food substances (sugars, fats, and 

 especially proteins) are present in too small amounts, and 

 for these we must look mainly to other articles of food. Pro- 

 teins are present in larger amounts in meats, eggs, cheese, 

 and in some seeds such as beans and peas. The food sub- 

 stances mentioned are present in different proportions in 

 different varieties of com. In flint corns, the part of the 

 endosperm next the embryo is closely packed mth starch 

 and is called the starchy endosperm; the part outside this, 

 which contains somewhat less starch and somewhat more 

 protein, looks clear and transparent, and is called the horny 

 endosperm. The homy endosperm does not shrink when the 

 kemel ripens, so that a kernel of flint com remains plump. 

 In dent corns, the starchy endospemi extends to the outer 



