98 BREEDING 



or wrinkled, if yellows and greens, and rounds and 

 wrinkleds occurred in equal numbers. But there 

 are three yellows to one green in every four, and three 

 rounds to one wrinkled in every four. And the 

 proportions in which each of the four combinations 

 occur is arrived at by multiplying together the ratios 

 in which each of the characters in a combination 

 occur separately : — 



A glance at Plate III. will show the kind of 

 approximation to the 9 ; 3 : 3 : 1 ratio which is obtained 

 in a small number ; there are thirty-eight seeds 

 altogether, and the various combinations of characters 

 occur in the following proportions : — 



18 Yellow round, 7 Yellow wrinkled, 12 Green round, and 

 1 Green wrinkled 



That is to say, there are too many green rounds and 

 too few green wrinkleds ; but deviations of this magni- 

 tude in so small a sample are of no significance. 



So far the visible characters of the plants — i.e. of 

 the cotyledons of the young plants seen through the 

 seed-coats — have alone been considered. The dis- 

 tinction between pure and hybrid individuals bearing 

 the dominant character has been left out of account. 

 It must now be considered. The simplest case is 

 that of the green wrinkled ; every one of these, 

 appearing in the second hybrid generation, will 



