10191 FIELD CROPS. 143 



Kansas, were grown in 100-ft. rows. The percentage of hard grains In each 

 group, together with the correlation between yield and percentage of hard 

 grains, is indicated in tabular form. 



The correlation between yield and hardness in the case of the durum varieties 

 was found to have a plus value, while that in the case of the other groups had 

 a minus value, indicating that the harder races would be eliminated within a 

 few years. It is concluded, therefore, that " the gradual softening of an impure 

 race of wheat [that is, commercial strains] can thus be explained as a climatic 

 selection without the necessity of assuming any direct or accumulative iutlu- 

 ence of the climate upon the hereditary substance itself. . . . An hereditary 

 distinction between the durum and Turkey wheat is thus brought to light, in 

 that the harder strains of Turkey wheat are much reduced in yield, whereas in 

 the durum wheats the harder strains are the better yielders. These hereditary 

 distinctions, though not striking in any one season, are sufficient to maintain 

 the hardness of the durum wheat and slowly change the other toward the con- 

 dition of softness and low nitrogen content usually found among bread wheats 

 which have been grown for a number of years in a warm climate. . . . 



" We must discard mixed commercial varieties and grow only pure races of 

 wheat coining originally from a single plant. ... It is highly important 

 that the seed wheat of the community be maintained in its standard of purity 

 through repeated pedigree selection. This work should be done either by the 

 State or by reputable, trained seed breeders, and from these the farmer should 

 renew his seed at least every four or five years." 



Producing bread-making wheats for warm climates, G. F. Freeman {Jour. 

 Heredity, 9 (1918), No. 5, pp. 211-226, figs. 5). — In connection with the studies 

 noted above the author, in an effort to obtain a high-grade milling wheat for 

 warm climates, describes reciprocal crosses made in 1913 between a white maca- 

 roni wheat coming originally from Algeria ; a soft red bread wheat also from 

 Algeria ; and Sonora, a soft white wheat grown locally. The inheritance of 

 grain texture is discussed, and tabulated data are presented showing the inher- 

 itance of this character through four generations. Microscopical studies of the 

 texture of the wheat grain were made by means of thin cross sections reduced 

 to the necessary transparency by polishing. Observations on the inheritance 

 of " yellow berry " in pure lines of hard wheat are also noted. 



The hardness of a wheat is said to be determined by the solidity of the 

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

 starch in the endosperm. With a sufficiently high ratio of gluten to starch, the 

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

 while in the absence of sufficient gluten the shrinkage does not fully compensate 

 for the loss of water, and air spaces appear within the cells which render the 

 grains soft and also serve as refracting surfaces, making the grains opaque. 

 Two types of soft grains were recognized among the wheats employed in these 

 experiments. " True softness " was represented by a type in which the air 

 spaces in the endosperm were diffuse and finely scattered, the type being only 

 slightly affected by environmental conditions. The second type, commonly 

 known as yellow berry, was characterized by air spaces within the endosperm 

 occurring in flakelike groups with quite definite margins, giving rise to opaque- 

 ness which might be confined to a small spot only or might include the entire 

 endosperm. This type was very sensitive to environic conditions. 



The results obtained in the hybridization work may be summarized as fol- 

 lows : The genetic behavior of true softness may be explained by two inde- 

 pendent factors which govern the relative proportion of gluten and starch. 

 These factors showed incomplete dominance over their absence, the intensity of 



