196 



BREEDING CROP PLANTS 



corn and gave 2.5 per cent, higher protein content. These 

 particular strains, 1 and 4, were not examined during the seedling 

 stage and consequently it was not then known that strain 1 was 

 heterozygous for the white seedling chlorophyll abnormality 

 which Lindstrom has designated by the factor w. In the second 

 generation grown from self-fertilized ears of A, B, and K, ap- 

 proximately one-fourth of the seedlings were pure white. Lind- 

 strom has shown that plants heterozygous for the chlorophyll 

 factors Ww are slightly less vigorous than homozygous green 

 forms. These facts lead one to expect that high protein races 

 with good yielding ability may be produced. On the other hand, 



FIG. 44. Two high protein strains of Minn. No. 13 at left and right respectively 

 which have been self-fertilized for five years and first generation cross between 

 them in the center. The Fi yielded slightly more than normal Minn. No. 13 and 

 analyzed 2^ per cent, higher in protein content. 



maximum yield of grain and high protein content probably can 

 not be obtained in the same variety. 



CORN IMPROVEMENT BY THE TRAINED PLANT BREEDER 



A uniform technic has been developed for the small-grain breeder. 

 With corn, however, the correct method of breeding is even yet 

 somewhat problematical. Investigations have helped to clarify 

 our ideas regarding the value of different methods of wcrk. 

 For the farmer the results obtained have tended to simplify pre- 

 vious ear-to-row methods. For the technical breeder, how- 

 ever, the application of Mendelian principles has resulted in 

 several plans, some of which appear rather complex. Their 



