166 



THE THEORY OF THE GENE 



similar cross, in which the pollen in F a was largely abor- 

 tive, there were large numbers of gemini present and 

 many single chromosomes. Results similar to these were 



# r 



w 



\W% 



Fig. 96. 



Maturation stages of several types of apogamous species of Hiera- 



cium. (After Eosenberg.) 



found in two other tetraploid crosses. In general, the 

 result with tetraploids shows that like chromosomes are 

 present in these different species that conjugate with 

 each other, or at least it seems more probable that the 



