THE MEXDELIAX PRINCIPLES OF HEREDITY 87 



o 



PARENTS 



Y R X / G~W 



O 



YR GW 



'YR 



YW 

 YW 



GR 

 GR 



GW 



GW. 



FIG. 47. Illustrating the history of the gametes of 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 iri the squares below. 



