E. R. Saunders 309 



91 of the resulting Fi crossbreds were self-fertilised to produce F,. 



The number of these ^i plants derived from the 6 rf-parents used as f^, 



representing in each case an equivalent number of pollen grains, were 



respectively 



57 

 19 



7 



8 



8 



8 



Total "91 



Doubles occurred in every F, family. Each of the 91 pollen grains 

 tested 7nust therefore have been carrying the double character. 



In the sulphur- white race 7 individuals were employed as the 

 rf-pollen-parent in matings with 9 individuals belonging to 3 different 

 pure-breeding strains. The number of seed-parents used in each case 

 was as follows : 



^o-d-glabrou8 cream 5 



flesh 3 



„ hoary white (Bromptou) 1 



Total ... 9 



93 of the crossbreds were tested as in the red race. The number of 

 these ^j plants derived from the 7 c?-parents were respectively 



22 

 22 

 16 

 15 



8 



7 



3 



Total "93 



Doubles were obtained in 90 out of the 93 families. It remains to 

 consider whether in the 3 families in which no doubles were recorded 

 their absence is probably real or not. It would seem that in two of the 

 three cases, at least, we may fairly regard the totals, viz. 8 and 17, as 

 too small to be conclusive, for we find among the mixed families a case 

 where the proportion of singles to doubles was as high as 20 : 1 (the 

 actual numbers were 40 s. 2 d.). This being so, it is clear that the two 

 cases in question fall within the range of what may be expecte«l from 



Joum. of Gen. 1 21 



