130 MENDELISM chap. 



produced so do the proportions of the eight possible 

 classes of plants differ. But the general rule already 

 laid down, that the majority of the gametes are of 

 the parental types, holds good here also. When 

 two factors go into the cross from the same parent 

 they show coupling in gametes produced by the F^ 

 plants : when they enter the cross from opposite 

 sides they exhibit repulsion when the F^ gametes 

 come to be formed. For example, in the cross of a 

 purple-hooded long with a red-erect round, BeL x bEl^ 

 there is coupling between the factors B and L but 

 repulsion between B and £", and between L and E. 

 The two commonest types of gamete formed are the 

 BeL and the bEl types. But there are also found a 

 few gametes of the other possible types, viz. Bel, 

 bEL, BEL, bel, BEl and beL, The last four types 

 are, however, extremely rare. So also in the cross 

 between an erect purple long and a hooded red 

 round, BEL x bel, all of the possible eight types of 

 gamete are found, but the two parental types 

 BEL X bel are far more numerous than any of the 

 others. This is evident from the nature of the F„ 

 generation, of which the following particulars for 

 1803 individuals are available : 



Erect 1 

 purple 

 long J 



(Hooded 

 red 

 round 



Erect purple long 



Erect Erect Hooded Hooded Erect Erect Hooded Hooded 



purple purple purple purple red red red red 



long round long round long round long round 

 1 196 100 7 5 3 7 112 yj-i, 



