172 HEREDITY AND SEX 



the reciprocal cross gives males and females in equal 

 numbers. Correns' interpretation is shown in the 

 lower part of the next diagram. 



Bryonia dioica and B. alba 

 B. dioica $ by B. alba $ B. alba 9 by B. dioica $ 



\ / \ / 



\ / \ / 



Females Females and Males 



Correns 1 Explanation 



F - F B. dioica (FM)-(FM} B. alba 9 



(FM ) (FM ) B. alba $ F - M B. dioica $ 



F(FM) female F(FM) female 



male 



It is based in the first case on the assumption that 

 the hermaphroditic condition of B. alba is recessive to 

 the dioecious condition of B. dioica, and that the female 



tlialeTf. -HcrmabH. FH 



i> H 



f H fwotv. -PH Txemv. 



"f" H Kerriv. ovtile 

 'F -p mate 



FIG. 88. Diagram to illustrate G. H. Shull's results on Lychnis dioica. 

 The symbols here used are not those used by Shull. Two types are assumed 

 not to appear, viz. HH and Hf. Third cross should give FH also. 



