230 THE AMERICAN NATURALIST [Vol. LI 



junction with those in Tables I and II, accord with the 

 idea of linkage between R and (r on a 4 : 1 basis, especially 

 since they deviate so widely from the 27 : 9 : 21 : 7 ratio of 

 independent inheritance. 



Another source of evidence on the genetic interrela- 

 tions of the R and G factors was noted in a back cross in 

 which the I factor for aleurone color was involved. No 

 aleurone tests have been made, but evidence from related 

 plants in pedigree cultures makes it seem reasonable that 

 the following factors are concerned : 



GgRrccAAPPIi ^ ggrrCcAAPPii 

 3021 (1) 3018 (10) ■ 



In this case, the ears of both parents showed no aleurone 

 color. The ear from the cross gave a distinct segregation 

 of purple and of colorless grains (36 purple: 195 color- 

 less), approximating the theoretical 1 : 7 ratio. Assuming 

 the factors as given above, this aleurone ratio is reason- 

 ably close to the expected proportion, the numbers being 

 relatively small. As a check upon this aleurone ratio, it 

 might be mentioned that six of the plans from purple 

 seed were self ed. Each one showed a 9 : 7 ratio of purple 

 to colorless grains on the ear (total, 1441 purple: 1088 

 colorless). Also three Fj plants from colorless seed were 

 selfed and the ears showed no aleurone color. 



The field counts of the plants from purple and from 

 colorless F^ grains are classified in the following table : 



TABLE IV 



Showing the Distribution from the Cross 

 GgRrccAAPPIi ggrrCcAAPPii 

 3021 (1) 3018 (10) ■ 



Here again, while the value for P is relatively small 

 (P — .1171), it is noted that in general the observed re- 



