837 



Tliese proportions suggest segregation according to three Mendelian 

 factors and this is also completely conlirnied by the proportion of 

 the second generation of' hybrids. By means of tlie character of the 

 red leaf-edge the "red" Cmma can therefore be represented as 

 AABBCC and the pnre green 6^ 11 as aahhcc. 



Since 7^4 (9 red and 4 green), 7^ 4— 1 (27 red and 10 green), 

 7? 4 — 1 — 1 (19 red and 7 green) and also the 4*'' generation 

 7^4 — 1 — 1 — 1 (10 red and 3 green) segregate according to 3:1, 

 R 4 must, at least if it is assumed that the three factors are inde- 

 pendent of one another, be heterozygotic for one of these three 

 and homozygotic for the other two, e.g. AaBBCC, which in the 

 following generation gives 1 AABBCC: 2 AaBBCC A aaBBCC. But 

 in that case descendants of 7? 4 must segregate according to 3:1 

 in so far as they are not pure "red" or "green". However 7^ 4 — 1—11 

 segregated as 9 : 7 (146 red and 123 green) and 7? 4 — 1 — 14 likewise 

 (53 red and 38 green) These can therefore be represented for example 

 as AaBbCC or AaBBCc, because they are clearly heterogyzotic for 

 two factors instead of for one. Since now ^4«56C6' cannot be directly 

 derixed from AaBBCC, we know that the representation AaBBCC 

 for 7^ 4 is incorrect and that R 4 also must have been heterozygotic 

 for at least two factors, but behaved as if this was so for only one 

 factor and that therefore in their Mendelian behaviour these t w o 

 factors were not independent of each other. 



If we apply this same reasoning to R 13 — 1, which in like 

 manner segregates as 8:1 (namely 20 red and 9 green), whilst 

 R 13 — J — 13 separates in the proportion 27 : 37 (7 red and 10 green) 

 then we come to the conchision that R 13 — 1 must have been 

 heterozygotic for three factors, therefore Aa Bh Cc, and nevertheless 

 behaved as a hybrid with only one lialf-representative factor, in 

 other words, the three facto r s were not independent 

 but correlated as if there were only the one. 



This is established by the second generation of crossing of "pure 

 red" with "pure green". All the specimens of F^ correspond to the 

 formula Aa Bb Cc. Yet segregation took place in 7^2, as was also 

 the case with the self-pollinated offspring of R-^ and 7^13, not only 

 according to 27 : 37, but also in the proportions 3 : 1 and 9 : 7, 

 a3 the following table shows. 



Probably it is no great error to say when considering all the 

 cases with more "green" than "red" individuals that they segregate 

 in the proportion of 27 red to 37 green, those with slightly more 

 "red" than "green" ones as belonging to those which segregate as 

 9 : 7 and thirdly, the cases with more than twice as many "red" 



