584 



If the position of the various determinants in the 

 chromosomes is definite, only slight variations in the de- 

 gree of association among hybrids between the same 

 parental strains would be expected, but there would be 

 no reason to expect that the different degrees of correla- 

 tion should fall into a definite series. 



Selective Pollination 

 From the standpoint of complete segregation or alter- 

 native inheritance of characters there remains the pos- 

 sibility of correlations being the result of selective pol- 

 lination. It is conceivable that the ovules which bear 

 one of the segregating characters are more readily fer- 

 tilized by pollen bearing another character with which 

 it was associated in the parent. As applied to our own 

 experiments, ovules which are potentially waxy might 

 be more readilv fertilized by pollen which is potentially 

 white. 



If correlations are the result of selective pollination, 

 no correlation should be shown as the result of crossing 

 an individual that is heterozygous with respect to both 

 of the character pairs with an individual showing both 

 of the recessive characters, for in such a cross the gam- 

 etes of one parent would be all of one kind. In our own 

 experiments, crosses between plants from hybrid seed 

 showing horny endosperm and colored aleurone (both 

 dominant characters) with plants from white waxy seeds 

 (both recessive characters) should throw light on tins 

 point. 



If the correlations result from numerical inequalities 

 in the classes of the gametes, the seed classes resulting 

 from such a cross as that described above should be the 

 same as the gametic classes produced by the heterozy- 

 gous parent. Thus, if the seed classes in a self-pollin- 

 ated ear correspond to those expected from a 3 : 1 ratio, 

 the same plant when crossed with a plant showing both 

 recessive characters should show classes in the ratio, 

 3 white-waxy, 1 white-horny, 1 colored-waxy, and 3 col- 



