336 



Douhleness in Stocks 



VII. Segregation in F^ cross-breds derived from unions between ever- 

 sporting and non-double-throwing forms, and statement of the results 

 obtained in F„. 



The various possible unions coming under this head are the 

 following : 



A. Eversporting form employed as seed parent 



In the case of matings 7 — 12 where the eversporting form is used 

 as the pollen parent we may expect eve7'y F^ family to yield doubles in 

 F^, whereas in the reciprocal unions (matings 1 — 6) some of the F^ 

 individuals may be expected to yield doubles and some to breed true 

 to singleness. Keference to Tables IV and V will show that such 

 was the case in each of the 8 types of union which have already been 

 carried out. 



With regard to the proportion of doubles occurring in those F^ 

 families which are mixed, it has been stated in the earlier accounts' 

 that they occur in the proportion of the simple Mendelian recessive, 



' loc. cit. 



