iq2o] COULTER— A LEU RONE COLOR 425 



3. In many cases the exact genotype, with reference to the R 

 and C factors, can be distinguished by superficial appearance. 



4. The particolored grains of East and Hayes were identified. 

 In these some partial substitute enables the P and R factors to 

 express themselves, even in the absence of C. This substitute is 

 heritable, but its effectiveness is limited by local conditions in 

 different parts of the ear or of the plant as a whole. 



5. Mottling (Emerson), which occurs when the R factor comes 

 in with the male parent only, is conditioned by the presence of a 

 heritable factor or factors. This factor occurs in the C tester 

 family, and is dominant in crosses with families which do not show 

 mottling. The R tester family seems to contain a different factor, 

 which produces apparent mottling only in a small percentage of the 

 expectations. 



University of Chicago 



