STUDIES ON THE GENETICS OF FLOWER-COLOURS, ETC. 
Ill 
stated. We liave therefore proven that we have in id the ratio 9 magentas : 3 
oranges : 4 whites, and we see that in this generation we have the complete 
linkage of It and B just as in Cross V. 
That the id-hybrid under discussion produces the gametes CUB, cRB, 
Ci'b, crb, but not CrB, cvB, CBb, CKb (except very rare cases, s. Table 
VI, B), will be seen also by crossing it back by white-I ( ccrrbb ), i. e. that 
variety which contains neither C nor It nor B, thus, for instance, this 
crossing was done in 1919, and we had in 1920 :— 
Magenta 
Orange 
White 
Total 
(White-! I x orange) x white-I 
27 
m 21 
36 
84 
Expected 
21+40 
21+4-0 
42+4-6 
84 
This cross indicates us clearly what kinds of gametes are produced by 
the id-hybrid, and from the results we see that B and It are completely 
linked to each other, because if the free assortment were the case, we should 
have the ratio 1 magenta : 1 red : 2 oranges : 4 whites instead of that 1 
magenta : 1 orange ; 2 whites, as it was actually the case. 
The experiment of Miss Yasui on the crossing of white and pale yellow, 
giving rise to magenta id-plants, 1 seems to agree with my present cross in 
several respects, though she has used pale yellow instead of orange. Though 
her experiment ends with id, the actual numbers of magentas, yellows and 
whites in the latter generation accords pretty well with the expected, and 
there will be perhaps no doubt that she had to deal in this generation with 
the 9:3:4 segregation. Her explanation in respect to the appearance of 
magentas in F x agrees also with what I have above stated about the same 
phenomenon ; the difference between her view and mine lies however in the 
fact that while she considers the magenta colour to be due to one single factor 
It (in co-operation with C), I regard the same colour to be due to the factor- 
complex III* (naturally in co-operation with C). Though from the analogy 
with several cases studied till now by many authors the combined action of 
some such factors for the production of the magenta colour seemed to me a 
i Bot. Mag., Tokyo, Vol. 34, 1920, pp. 59-63. 
