202 Certain Characters in the Cowpea (Vigna sinensis) 



The relation of B and E has already been dealt with, and it was 

 shown that these two factors repel each other in gametogenesis. The 

 relation between the factors B and P will now be discussed. 



The cross Black (Bp) by Purple Pod (bP). 



The Fi. The F^ possessed black seeds and purple pods, though the 

 colour of the pod was less intense than that of the purple podded 

 parent. 



The F^. In the F^ three types appeared, viz. BP, Bp, and bP. 

 Classifying the F^ the results were : 



Plants BP Bp bP 



273 168 40 65 



Taking the ratio of B to b we obtain 208 : 65 (expectation 205 : 68), 



while the ratio of P to p is 233 : 40 (expectation 205 : 68). 



The F,. 



1. Progeny of black, purple-podded F^ plants. 



Here the ratio of B to b is 434 : 122, and P to p is 427 : 129. The 

 expectation in both cases on a 3 : 1 basis is 417 : 139. 



2. Progeny of non-black, purple podded F2 plants. 



Families Plants BP Bp bP 



23 1036 1036 



3. Progeny of black, non-purple podded F2 plants. 



The main conclusions which may be arrived at from a survey of 

 these results are : 



1. The ratio of black to non-black in both F^ and F3 cultures is close 

 to 3:1, confirming the conclusion previously arrived at that black is 

 allelomorphic to its absence. 



2. The ratio of purple pod to non-purple pod in F^ is somewhat far 

 removed from 3:1, being 5*9 : 1*0, although in the segregating Fg families 

 the 3 : 1 ratio is more closely followed. Thus it is not certain that 

 purple pod is due entirely to a single factor P. This conclusion was 

 arrived at from a study of other crosses. 



3. The non-appearance of the double recessive non-black, non- 

 purple pod in the F^ and F3 cultures of the cross Bp by bP, indicates 

 that these two factors are repelled on a basis probably higher than 7 : 1. 



