136 



Outline of Genetics 



PARENTi 

 RACE ; SPOROPHYTE: 

 A 



® 



( 







GAMET0PHYTES:1 



(FERTILE) 



(FERTILE) 



PARENT) 

 RACE f SPOROPHYTE: 

 B 



GAMETOPHYTES:/ 



(FERTILE) 



(FERTILE) 



F, 1 SPOROPHYTE; 



GAMETOPHHES: 



(FERTILE) 



(FERTILE) 



(STERILE) 



(STERILE) 



Fig. 21. — Diagram illustrating Belling's explanation of semi- 

 sterility. 



