240 HEREDITY AND ENVIRONMENT 



27:9:9:9:3:3:3:1, etc. Thus when Mendel 

 crossed a variety of peas bearing round and 

 j^ellow seeds with another variety having 

 wrinkled and green seeds all the offspring of 

 the Fi generation bore round and yellow seeds, 

 round being dominant to wrinkled, and yellow 

 to green. But the plants raised from these 

 seeds, when self-fertilized, yielded seeds of 



RIW) R(W) RIW) R(W1 

 _R ^__ 



Fig. 53. Monohybrid Diagram showing results of crossing 

 round (R) seeded with wrinlsled (W) seeded peas. Large cir- 

 cles represent zygotes, small ones, or single letters, gametes. 

 In Fj all individuals are round but contain round and wrinkled 

 gametes. In F^ the cJ gametes are placed above the square, 

 the $ ones to the left, and the possible combinations of (J 

 and 2 gametes are shown in the small squares, the relative 

 numbers of different types being 1 RR:2 R(W):1 WW. 



