THE MENDELIAN PRINCIPLES OF HEREDITY 87 





PARENTS 

 Y R X X G W 



Fi 



YR GW 



, ,.--^*-^ 'YR 



YW 

 YW 



GR 

 GR 



GR 

 YR 



GW 



YR 



YR 

 YW 



o 



/ 



YR 



GR 



YW 

 6R 



GW;<K"" 



YR 

 GW 



Fig. 47. — Illustrating the history of the gametes ol the cross represented 

 in Fig. 46. The composition of the parents YR and GW and of the Fi hybrid 

 YRGW is given above. The four classes of ovules and of pollen are given in 

 the middle of the figure. These by random combinations give the kinds of 

 zygotes represented in the squares below. 



