196 Certain Characters in the Cowpea (Vigna sinensis) 



The cross red by white may be represented as nR x Nr, the types 

 appearing in F^ being : 



9NR 3nR 3Np Inn 



Buff Ked White White 



(6) The cross Black by White. 



A cross between a black and the white variety Para gave F^ black. 

 In F2 segregation occurred into black, buff, and white in proportions 



No F3 families were grown, but the F^ data, together with the 

 information acquired from the cross of red by white, enable a satisfactory 

 explanation of the results to be made. 



Two factors are concerned in the cross black by white. 



R the factor for red. 



B the factor for black, which is without visible effect except in pre- 

 sence of R. 



The factor for buff, N, is common to both parents. The cross may 

 be represented thus : black (BNR) by white (bNr), the types appearing 

 in F^ being : 



9BNR 3BNr 3bNR IbNr 



Black White Buff White 



From the results of this experiment it will be seen that factor M is 

 not necessary for the production of black. 



(c) The cross Black by Buff. 



The plants of the Fi showed complete dominance of black. Some of 

 the seeds were slightly mottled, and in these the ground colour was 

 seen to be buff. 



The F2. The results of the F^ are set forth below. Segregation 

 occurred into black, buff, and red, in proportions suggesting the 12 : '3 : 1 

 ratio, though the fit is not very close. 



