CORN GUOWEKS ASSOCIATION, 9I 



tlien be planted if desired. The wide variation in the composition be- 

 tween different ears furnishes a starting point for the selection of seed 

 in any of the several different lines of desired improvement. 



The methods of making a chemical selection of ears of seed corn by 

 a simple mechanical examination of the kernels is based upon the fact 

 that the kernel of corn is not homogeneous in structure, but consists of 

 several distinct and readily observable parts of markedly different chem- 

 ical composition. (See illustrations.) Aside from the hull which sur- 

 rounds the kernel, there are three principal parts in a grain of corn : 



1. The darker colored and rather hard and horny layer lying next 

 to the hull, principally in the edges and toward the tip end of the 

 kernel, where it is about 3 millimeters, or ys of an inch, in thickness. 



2. The white, starchy-appearing part occupying the crown end of 

 the kernel and usually also immediately surrounding, or partially sur- 

 rounding, the germ. 



3. The germ itself which occupies the central part of the kernel 

 toward the tip end. 



These different parts of the corn kernel can be readily recognized 

 by merely dissecting a single kernel with a pocket knife, and it may be 

 added that this is the only instrument needed by anybody in making a 

 chemical selection of seed corn by mechanical examination. 



The horny layer which usually constitutes about 65 per cent of the 

 corn kernel contains a large proportion of the total protein in the kernel. 



The white, starchy part constitutes about 20 per cent of the whole 

 kernel, and contains a small proportion of the total protein. The germ 

 constitutes only about 10 per cent of the corn kernel, but, while it is 

 rich in protein, it also contains more than 85 per cent of the total oil 

 content of the whole kernel, the remainder of the oil being distributed 

 in all of the other parts. 



By keeping in mind that the horny layer Is large in proportion and 

 also quite rich in protein, and that the germ, although rather small in 

 proportion, is very rich in protein, so that these two parts contain a 

 very large proportion of the total protein in the corn kernel, it will be 

 icadily seen that by selecting ears whose kernels contain more than the 

 average proportion of germ and horny layer we are really selecting 

 ears which are above the average in their protein content. As a matter 

 of fact, the method is even more simple than this, because the white 

 starchy part is approximately the complement of, and varies inversely 

 as the sum of the other constituents ; and to pick out seed corn of high 

 protein content it is only necessary to select those ears whose kernels 

 show a relatively small proportion of the white, starchy part surrounding 

 tht germ. 



