270 



two years, but very difficult in that of the nuts, which require al 

 least a human generation for the exhibition of any importani 

 effects of cross-breeding and other cultural improvements. 



Let us now very briefly consider the structural relationships 

 between the two classes. Both the grain and the nut are fruits 

 and not seeds. Each contains a single seed, but the wall of the 

 fruit (as to the ovary) does not open at maturity to provide for it; 

 escape. It is true that the outer portion of the chestnut, namely 

 the bur, opens to discharge the nuts, but this bur is an involucre 



flower. The hull of the hickory, which also separates into foui 

 parts, is by most botanists regarded as the calyx of the flower. 

 but it is not clear that it is not really a four-leaved involucre, like 

 the chestnut bur, simulating a calyx merely because it surrounds 

 but one pistillate flower. 



However, these points in reference to the involucre do not 



This fruit, in case of the grasses, is a grain, known to the bot- 

 anist as a caryopsis, the wall of the ovary being so tightly ad- 

 herent to the seed as not to be readily separable from it. In the 

 nut, although the seed, commonly called the kernel, entirely fills 

 the ovarian cavity, it does not adhere to the walls of the ovary, 

 and the two are readily separated in the shelling process. 



Comparing the two from a nutritive standpoint, we note that 

 the grains are admirably adapted to use as bread-stuffs, because 

 their starchy nature makes them readily ground into meal 01 

 flour. All of them contain from one-half to two-thirds, in sev- 

 eral cases more, of their weight of starch. All of them, more- 

 over, are poor in fat or fixed oil, which is another necessity for a 

 substance which is to yield a good flour. Even oats and corn, 

 which, because of their larger percentage of fat, are not readily 

 converted into fine flour, contain only 6 per cent, to 7 per cent. 

 of it. In wheat, rye and barley it ranges from 1.5 to 2.5 pel 

 cent., while in rice there is less than 0.5 per cent. In the most 

 important and physiologically valuable class of nutrients, namely 

 the albuminoids, the grains are markedly rich. Even rice, the 

 poorest of them, contains about 8 per cent. Corn and barlej 



