58 



EVOLUTION AND GENETICS 



the proportion of 1:2:1. All of these had the same 

 ancestry, yet they are of three different kinds. If 

 we did not know their history it would be quite im- 

 possible to state what the ancestry of the white or of 



r 



9' 



Vr 



"'A- 







Fic. 17. — Inheritance of color in the four o'clock (Mira- 

 hilis jahipa). The figure above and to the left stands for 

 a red flower, that above and to the right for a white flower. 

 The next two generations are shown below. 



the red had been, for they might just as well have 

 come from pure white and pure red ancestors re- 

 spectively as to have emerged from the j^hik hybrids. 

 Moreover, when w^e test them we find that they are 

 as pure as are white- or red-flowering plants that 



