I50 



Gametic Coupling 



[CH. 



The result of extensive counting shows that an approxi- 

 mation to the observed numbers would be produced by a 

 gametic system of such a kind that the combinations of long 

 pollen with blue factor, and round pollen with no blue factor 



n 



m 



IV 



Fig. 19. Pollen-grains of Sweet Pea. 

 The normal long (dominant) type is shown in II and IV: the 

 peculiar round type (recessive) in I and III. The upper figures 

 represent the dry condition. The lower figures show the appearance 

 in sulphuric acid, which makes the pores visible. Three-pored and 

 one-pored grains sometimes occur among the rounds, but they are 

 usually two-pored. In IV one of the grains is seen end-on, and in I 

 three of the disc-like grains are seen edge-wise. 



