CH. IX] Gametic Coupling 1 4^ 



Emily Henderson having romid ^^oW^Vi. The F^ generation 

 was a reversionary purple bicolor, with long pollen — for 

 the long pollen-shape is dominant — and from this the F ^ 

 generation was raised which consisted of 



27 purples : 9 reds • 28 whites. 



^- , ^ 



36 : 28 



9 7 



It has been shown that the interrelations of these several 

 types proved that the colour in both purples and reds 

 is due to the simultaneous presence in the zygote of two 

 factors which we have called C and R, and that the white- 

 flowered plants are those in which one or both of these 

 factors are absent. The point, however, which now con- 

 cerns us more immediately is the distinction between the 

 purples and the reds. This, we have seen, is due to the 

 presence or absence of a factor B^ blue. Those coloured 

 plants which have the factor B are purple, those devoid 

 of this factor B are red-flowered. 



We saw also that there were various subordinate classes 

 among the purples with corresponding subordinate classes 

 among the reds, each due to the possession or to the want 

 of some special factor. These differences are similarly 

 distributed among the purples and among the reds. For 

 example if the family is one which contains picotee types, 

 there are picotees among the purples and corresponding 

 types among the reds, and in each colour-group the pro- 

 portions are the same, averaging 3 fully-coloured to i 

 picotee in the case of the purples and the same in the case 

 of the reds. 



When however the distribution of the pollen-characters, 

 long and round, in a family containing purple, red, and white 

 members is examined, it is found that taking the family as 

 a whole the long-pollened plants are to the round-pollened 

 as 3 to I in the usual way. Among the white-flowered 

 also there are 3 longs to i round. But when the purples and 

 the reds are separately studied, the numbers 3 long : i round 

 are not found. On the contrary, in the purples there is a 

 great excess of longs, which are to the rounds as about 

 12 to I, while among the reds there is an excess oj rounds, 

 which are to the longs as about 3*2 to i. 



