NEO-MENDELISM IN PLANTS 425 
accord with the conceptions that have been presented, and only two 
assumptions are necessary: (1) that dominance is absent, and two 
doses have twice the effect of one: (2) that the independent similar 
factors are cumulative in their operation, and are paired with their 
absence in the hybrid. This was Nilsson-Ehle’s conception, and of 
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Fic. 84.—Diagram illustrating Nilsson-Ehle’s explanation of 15:1 ratio 
obtained in F, generation from cross between red-grained and white-grained 
wheat. (From Coulter and Coulter.) 
course he tested it by further experimental work, the results consist- 
ently confirming the conception. 
Since it is important to fix this conception clearly in mind, another 
type of diagram may represent the facts even more clearly. The 
proportion of individuals showing the various degrees of redness in the 
F, is graphically recorded in Fig. 85, each dot representing one dose 
of the factors in question. 
