THE DISTRIBUTION OF CHARACTERS 543 



tL*,^;,^''^^""' S^f ^^ti«°«- Throughout a number of genera- 

 tions the behavior of tallness and dwarfness was carefully recorded. 

 In this way he studied a number of pairs of contrasting characters 

 such as: (1) shape of pod (whether simply inflated or deeply 

 constricted between the seeds); (2) color of unripe pod (whether 

 green or yeUow); (3) distribution of flowers on the stem (whether 

 distributed along the axis of the plant or bunched at the top); 

 (4) color of cotyledons (whether yellow or green); (5) shape of 

 seeds (whether round or wrinkled); and (6) color of seed coat 

 (whether gray or brown, with or without violet spots, or white) 

 The Distribution of Characters. — Mendel found that in most 

 cases the different pairs of characters investigated behaved in 

 the same regular way in the successive generations. Further- 

 more, it made no difference as to which variety was used for the 

 mother parent. In case of tallness and dwarfness, all the plants 

 of the first or F, generation were tall. They were all like the 

 tall parent. In the second or F, generation there were both tall 

 and dwarf plants, but there were three times as many tall plants 

 as dwarf ones, the tails and the dwarfs occurring in the ratio of 

 3:1. The offspring of the dwarfs were all dwarfs in the third or 

 Fi generation and in all succeeding generations. The dwarfs, 

 therefore, were pure for dwarfness, that is, they had no factors 

 or genes for tallness in them. One out of every three tall plants, 

 also bred true, and therefore, proved to be pure for tallness, but 

 two out of every three tall ones gave three times as many tall 

 ones as dwarfs or a ratio of 3 : 1, thus being apparently the same 

 in constitution as each of the individuals of the Fi generation. 

 They evidently contained factors or genes for both tallness and 

 dwarfness. The dwarfs and one-third of the tall ones of the 

 Fi progeny, bred true, while two-thirds of the tall ones again 

 bred as in the previous generation, giving the ratio 3:1, and two- 

 thirds of the tall ones being impure. This proved to be a constant 

 way of behaving throughout generations. The character of the 

 individuals of the different generations are shown in Figure 476. 

 Thus by the further breeding of the second hybrid generation, it 

 was found that, although the tails and the dwarfs were in the 

 ratio of 3 : 1 in the second hybrid generation, there were in reality 

 three Icinds of plants, pure tails, impure tails, and pure dwarfs, 

 occurring in the ratio 1 :2 : 1, and that the impure tails always 

 produced three kinds of plants in the same ratio of 1 : 2 : 1. 



