i8o 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 2 )* 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 



white x yellow (50 %) (50 %) white x white 



F 3 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 x is the first genera- 

 tion of offspring the cross-bred seeds and the plants to 

 which they give rise. To the F 2 generation belong the seeds 

 produced upon the F l plants, and the plants to which they 

 give rise, and so on. 



