42 BULLETIN 1074, U. S. DEPARTMENT OF AGRICULTURE. 



mottled, the condition being designated as "yellow berry," and are 

 then rather soft. 



The difficulty of the numerous investigators in determining the 

 kernel texture has been due to the failure to dissociate softness from 

 starchiness or yellow berry. Freeman (91) has shown the nature 

 of hardness in the wheat kernel. The following is quoted from 

 his conclusions: 



1. The hardness of a wheat is determined by the solidity of the grain, and 

 this, in turn, by the nature and relative proportions of gluten and starch in 

 the endosperm. 



2. When the ratio of gluten to starch is sufficiently high, the entire cell 

 contents are cemented together solidly as the grain dries out in ripening. 

 It, therefore, takes on a hard, glassy, semitranslucent texture. In the ab- 

 sence of a sufficient proportion of gluten to hold the cell contents together, 

 the shrinkage in drying does not fully compensate for the loss of water, and 

 air spaces appear within the cells. These open spaces render the grain soft 

 and, also, since they serve as refracting surfaces, make it opaque. We are, 

 therefore, accustomed to associate softness, opaqueness, and low gluten con- 

 tent in wheats. 



3*. There are two types of soft grains among the wheats included in these 

 experiments. 



(a) A type designated by the writer as "true softness," in which the 

 air spaces in the endosperm are diffuse and finely scattered. This type 

 of softness is only slightly affected by environic conditions. 



(&) A type commonly called "yellow berry," in which the air spaces within 

 the endosperm occur in flakelike groups with quite definite margins. The 

 opaqueness thus arising may be confined to a small spot only or may include 

 the entire endosperm. This type of softness is very sensitive of environic 

 conditions. 



In this bulletin soft texture refers to the condition designated above 

 as " true softness " and must not be confused with yellow berry. 



True kernel texture, therefore, can not be determined on yellow- 

 berry kernels, because they always are soft. It usually is possible, 

 however, to select from a sample a few kernels which are not wholly 

 starchy and which can be accurately used for texture determinations. 

 Eoberts {159) has attempted to measure hardness mechancially by 

 determining the crushing strength. This is not entirely accurate, 

 as the shape of the kernel influences its crushing strength and, in 

 addition, so ft- wheat varieties grown under dry -land conditions are 

 quite brittle and difficult to crush. Texture is determined by cutting 

 kernels which are not affected by yellow berry and examining the 

 endosperm. 



SHAPE OF THE KEENEL. 



The shape of kernel outline is described as ovate, elliptical, or 

 oval. These terms refer only to the outline of the kernel as viewed 

 from the dorsal surface, and not to the kernel as a whole. When 

 egg-shaped in outline, the germ end being the broader, it is described 



