INDEPENDENT MEN DELI AN INHERITANCE 83 



white. When the endosperm segregation into starchy and sweet is taken 

 into account in the same hybrid the segregation will be in the ratio of 

 3 starchy : 1 sweet in each of these classes, for these characters segregate 

 independently of the aleurone color. This gives, therefore, 3 purple 

 (3 starchy : 1 sweet) : 1 white (3 starchy : 1 sweet) which becomes on 

 expansion 9 purple starchy : 3 purple sweet : 3 white starchy : 1 white 

 sweet. 



The correlation of the above facts with chromosome behavior is 

 again very simple. The factors W and w lie in identical positions in one 

 pair of chromosomes and the factors S and s lie in identical positions in a 

 different pair of chromosomes. If the difference between the two varie- 

 ties of maize is only in these factors, then all the other pairs of chro- 

 mosomes in the varieties bear the same set of factors. Accordingly of 

 the ten pairs of chromosomes of maize only those two need be considered 



FIG. 39. Chromosome behavior in reduction in Fi from a cross between purple 

 sweet and white starchy corn. Factor symbols: w = white, W = purple, s = sweet, 

 S = starchy. 



which bear the above factors. The relations then are shown diagrammat- 

 ically in Fig. 39. The parents in both cases produce gametes which are 

 all alike. The crossing of these parents produces a zygote in which two 

 pairs of the chromosomes differ in their factor content. One member 

 of one pair bears W and the other w and in the other pair one member 

 bears S and the other s. Two types of F t reduction division are 

 possible and these give four kinds of gametes as shown in the diagram. 

 Since this has occurred in the formation of both ovules and pollen grains, 

 in the self-fertilization of such a plant there are sixteen possible combina- 

 tions of gametes, which distribute themselves in four phenotypes in the 

 ratio 9 purple starchy: 3 purple sweet: 3 white starchy:! white sweet. 

 This feature of the case has already been discussed fully and need not be 

 repeated here. 



The actual agreement of this analysis with experimental results 

 has been shown by several investigators but particularly by East and 

 Hayes. In one case they crossed a white flint corn, Rhode Island White 

 Cap, with a purple sweet corn, Black Mexican. The F\ grains were 

 purple starchy and in F 2 there was sharp segregation for purple and white 

 aleurone and starchy and sweet endosperm. In some cases splashed 



