122 MENDELISM 



CHAP. 



The purple longs form about one half of the total, 

 the purple rounds and the red longs each form 

 about one quarter, while the red rounds are ex- 

 tremely rare. Far fewer plants have been raised 

 from this mating than from the preceding one, but 

 the appended scheme, in which are given the actual 

 figures obtained, shows clearly how widely they 

 depart from the former case. 



Purple round x Red long 

 Purple long 



Purple long Purple round Red long Red round 

 226 95 97 I 



Here again we can explain these peculiar pro- 

 portions by a simple assumption. If we suppose 

 that the F^ purple, arising from the cross between a 

 purple round and a red long, forms a series of 

 gametes of the nature i BL : y Bl : 7 bL : i bl, 

 instead of in equal numbers, we can understand the 

 peculiar proportions in which the four classes of the 

 F^ generation appear. For such a series of ova 

 fertilised by a similar series of pollen grains will 

 give a generation of the following composition : 



I BBLL + 7 BBLl+7 BbLL+ i BbLl 

 4-7 BBLl+7 BbLL + ^g BbLl 



+ 49 BbLl 

 + I BbLl 



129 purple long 



+ 49 BBll^-j Bbll^-^c) bbLL + y bbLl-\- 1 bbll 

 + 7 Bbll + 7 bbLl 



63 purple 63 red i red 



round long round 



