INHERITANCE IN MAIZE 181 
The pollen of the F, plants (¢.e., those plants which 
were derived from the yellow cross-bred grains)—when 
applied to the female flowers of the same pure white 
strain of maize, caused in like manner the appearance 
of white and yellow grains in equal numbers. This 
result is equally well expressed by the above diagram 
on simply regarding the yellow in F, as the male parent 
(pollen-parent) instead of as the female parent (seed- 
parent) of F,. 
What is, then, the meaning of these results? The 
case is really very simple. The germ-cells (ova and 
pollen-nuclei) of the cross-bred plants (white x yellow) 
must be potentially either pure white or pure yellow, 
with no blending of these characters. Further, the 
two kinds (yellow and white) of male germ-cells or 
pollen-nuclei must arise in equal numbers, and the 
same must be true of the female germ-cells or ova. 
By this supposition only can the observed facts be 
explained. If the supposition is true, then, when the 
cross-bred plant (F,) is crossed again with the pure 
white form, its white germ-cells give rise to white 
grains which are of the nature (white x white), and 
are therefore pure. Its yellow germ-cells give rise to 
yellow grains which are of the nature (yellow x white). 
And, since the number of yellow- and white-bearing 
germ-cells is equal, the number of yellow and of white 
grains produced in this way is approximately the same. 
The yellow grains are of the same composition as the 
original cross-bred grains obtained by crossing pure 
white with pure yellow, and we have seen that they 
behave in exactly the same way on further cross- 
