180 MENDELISM 
Half the grains, then, of the parentage (white x 
yellow) x white are pure white in colour, and not to be 
distinguished from grains of the parentage white x white 
even after an extensive examination of their offspring, 
which is the most rigorous test we are able to apply. 
The yellow grains born upon the same hybrid plants 
(F,)* had clearly each of them one white parent— 
namely, the plant from which the white pollen was 
derived. On sowing these yellow grains and once 
more pollinating by pure white, a precisely similar 
result was observed to that obtained in the preceding 
generation—that is to say, these plants, derived from 
yellow grains, produced once more 50 per cent. of 
white grains and 50 per cent. of yellow. We are, 
therefore, led to suppose that the yellow grains born 
upon the hybrid plants are of precisely the same nature 
as the original yellow hybrid grains (white x yellow), 
since their behaviour when pollinated from the same 
white strain is identical. We may express the result 
so far obtained in the form of the following diagram ; 
p* white x yellow 
F, yellow x white 
| | ; 
F, white x yellow (50 %) (50 %) white x white 
| ) | 
F,; white(50%) yellow (50 %) white (exclusively). 
* The following shorthand expressions are adopted to denote 
the different generations in cross-breeding experiments: P is 
the generation of the original parents ; F, is the first genera- 
tion of offspring—the cross-bred seeds and the plants to 
which they give rise. To the F, generation belong the seeds 
produced upon the F, plants, and the plants to which they 
give rise, and so on. 
