Neo-Mendelism 65 



This shows a regular dihybrid ratio, except that the 

 two factors involved are similar. Applying the single 

 dose and double dose conception, as used in the case of 

 Corren's pink Mirabilis, we reach the following con- 

 clusions: no. I only has four doses and therefore it only 

 is deep red; nos. 2, 3, 5, 9 have three doses and are some- 

 what lighter red; nos. 4, 6, 7, 10, II, 13 have two doses 

 and are still lighter red; nos. 8, 12, 14, 15 have one dose 

 and are very light red; while no. 16 alone has no dose 

 and is the only pure white. This accounts for the 15: i 

 ratio, and the different shades of red. This is entirely 

 in accord with the conceptions that have been presented, 

 and only two assumptions are necessary: (i) that domi- 

 nance is absent, and two doses have twice the effect of 

 one; (2) that the independent similar factors are cumu- 

 lative in their operation, and are paired with their 

 absence in the hybrid. This was Nilsson-Ehle's 

 conception, and of course he tested it by further experi- 

 mental work, the results consistently 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. 15, each dot representing 

 one dose of the factors in question. 



Continuing these investigations, Nilsson-Ehle next 

 discovered a new strain of red-grained wheat, which, 

 when crossed with the pure white strain, yielded F, 

 hybrids of intermediate intensity of red as before. 

 The F2 generation, however, showed a different situation. 

 Reds and whites were obtained in the proportion of 



