188 KARL B. KRISTOFFERSON 
found in the above that the red factor R in Aquilegia has also such 
an effect. This factor shows then both isophene and heterophene 
pleiotropism. However, an absolute coupling between two factors is 
also able to give the impression of pleiotropism. In the case, cited 
above, of the inhibiting yellow factor in oats absolute coupling between 
two factors would also explain the matter. Indeed many cases of 
supposed heterophene pleiotropism will probably turn out to be 
coupling phenomena, when closely investigated.  Heterophene 
pleiotropism may of course also exist. The individual observed is 
the result of the reaction of the »Gesamtgenotypus» with the environ- 
ment as JOHANNSEN points out so often and it appears most 
probable that a certain factor influences several organs even if it is 
too vague to be readily seen in some of them. The above experiments 
do not show, however, whether the heterophene pleiotropism of the 
red factor in Aquilegia is real pleiotropism, or whether it is a case 
of coupling between the colour factors and the factors for lenght of 
the stalk etc. 
THE REMAINING SEGREGATIONS INVESTIGATED 
IN AQUILEGIA. 
In addition to the above mentioned factors I have found another 
factor, C, influencing the distribution of colour in the corolla. In a 
cross between a dark-blue and a white type a Fi-generation of 35 
dark-blue individuals was obtained; 18 of these had the corolla self- 
coloured, and 17 had the margins of the petals white. The white- 
marginated bred true in F2. The progeny of 3 self-coloured F;-plants 
were examined in Fa. They showed segregation in 63 self-coloured 
and 20 white-marginated; consequently almost exact the ratio 3: 1. 
When the factor C is present it gives self-colour to the petals; when 
it is absent the petals become white-marginated. The effect of this 
factor is seen in the dark-blue and the red types, and only these have 
been used in determining the ratio of the segregation. In the light- 
blue types it is impossible to see whether the factor C is present or 
not. In the white-flowering plants it has no visible effect at all, 
of course. 
I have also examined some other segregations. I have found no 
less than 6 nuances of blue and 6 nuances of red in all. They are 
rather easy to distinguish — the variation seems to be quite discontinous 
— but the number of individuals was too small to permit a determina- 
tion of the genetical factors involved in these complicated segregations: 
