A Genetic Study of Plant Height in Phaseolus Vulgaris. 61 
facts with reference to the inheritance of habit of growth — so that 
the combination shall afford a true picture of the results secured 
from a cross between a tall pole bean and a short bush bean, 
or a short pole bean and tall bush bean. Let us assume that 
difference in habit of growth between pole and bush beans is 
due to the single factor A and that the difference between a tall 
bush bean and a short one or between a tall pole bean and a 
short one is due to the two factors B and C. Let us also assume 
that A is a dominant factor and that B and C are nondominant 
factors. Finally, the following values, which are to be added 
to an initial value of three internodes, will be assumed for the 
three factors: 
A = 10 internodes 
B= 1 internode 
C = 1 internode 
Because A is dominant and B and C are nondominant, these 
factors, when in the duplex condition, will have the following 
values: 
AA = 10 internodes 
BB = 2 internodes 
CC = 2 internodes 
A plant with the formula AABBCC is then — environmental 
influence aside — a pole bean with 17 internodes, a plant AAbbcc 
is a pole bean with 13 internodes, a plant aaBBCC is a bush 
bean with 7 internodes and a plant aabbcc is a bush bean with three 
internodes. A cross between AABBCC and AAbbcc would give an 
Fo of all pole beans but with a somewhat greater range of varia- 
tion than that of either parent. Likewise a cross between aaBBCC 
and aabbcc would produce nothing but bush beans, but the varia- 
tion in Fs would be greater than in either parent. Crosses be- 
tween AABBCC and aaBBCC, between AAbbcc and aabbcc, 
between AABBcc and aaBBcc, etc., would give, in F2, three pole 
beans to one bush bean without an increased range of variation 
in either class over that of the parent races. Finally a cross be- 
tween AABBCC and aabbcc or between AAbbcc and aaBBCC 
would result in Fo in three pole beans to one bush bean and both 
of the F2 classes would show greater variation than the parent 
races. The latter possibilities alone need be illustrated further. 
The formulae and numbers of internodes of the parents and Fi 
would be: 
Parent AABBCC = 17 internodes. 
Parent aabbcc = 3 internodes. 
Fi AaBbCc =15 internodes. 
Or: 
Parent AAbbcc = 13 internodes. 
Parent aaBBCC = 7 internodes. 
Fi AaBbCc =15 internodes. 
