6o BREEDING 



plant. Indeed, not only can the colour of the 

 cotyledons be seen before the seed is sown, it must 

 be seen then, or not at all, inasmuch as it cannot 

 be seen for long after the seed has begun to germinate, 

 because as the growing plant absorbs the food- 

 material in the cotyledons, their colour fades. But 

 it could still be clearly seen in the seedlings represented 

 in Fig. 19. 



Stated in general terms, therefore, the second 

 hybrid generation consists of three plants with yellow 

 cotyledons, and one with green, in every four. In 

 practice this result is seen in the existence of yellow 

 and green peas in the ratio of three to one in the 

 pods of a plant of the first hybrid generation. In our 

 imaginary cross made in the summer of 1910 the 

 numbers of these yellow and green seeds could be 

 counted in the autumn of 1911. These seeds would 

 be sown in the spring of 1912. It would be found 

 that the green seeds produced plants on which all 

 the seeds were green ; that one of every three yellow 

 seeds would produce a plant on which the seeds were all 

 yellow, and that the remaining two yellows would 

 produce plants which would bear yellow and green 

 seeds in the ratio of about three to one. Stated in 

 more general terms, this means that of every four 

 plants (on the average) of the second hybrid genera- 

 tion : one (recessive) plant with green first two 

 " leaves " gives rise solely to plants like itself when 

 it is allowed to self-fertilise ; two (hybrid) plants 

 with yellow first two leaves will produce plants with 

 yellow, and plants with green first two leaves, in the 



