HEREDITY AND EVOLUTION 
243° 
white-grained corn which, when crossed, will give all red grains 
in the F, generation. In the #, generation there will be nine 
red to seven white. This 
ratio suggests at once 
that here is a case of 
the inheritance of two 
factors. In such a case 
nine out of sixteen indi- 
viduals have both dom- 
inants of two pairs of 
allelomorphs. 
Two factors were nec- 
essary to produce the red 
color, and one of these 
was present in one of the 
strains and the other in 
the other strain. When 
these two strains were 
erossed, all the individ- 
uals in the F, generation 
eontained both factors 
and so were red. In the 
F, generation nine of the 
sixteen individuals con- 
tained both factors that 
were necessary for color 
and so were red, six con- 
tained one or the other 
of the two factors and 
were white, while one did 
not contain either of the 
two factors and so was 









, 
Abt cEhe cE 
s--C Cie Ce 
Fig. 236. Diagram of inheritance of com- 
plementary factors producing a red color 
in corn 
The complementary factors are dominant and 
are represented by C and E, while their 
absence is shown by c and e respectively. 
Each parent has only one of the complemen- 
tary factors and is white, while the F, hybrid 
has both factors and is red. The red color in 
the grain is indicated by stippling 
white. Two factors, both of which are necessary for the produc- 
tion of a single character, are known as complementary factors. 
The inheritance of the factors in the above case is shown in 
Fig. 236, in which one of the necessary factors is represented 
