542 



HEREDITY 



FIG. 476. A diagram illustrating Mendel's discovery concerning the in- 

 heritance of tallness and dwarf ness in the Garden Pea. At the top are the 

 parents of the cross, the tall variety at the left and the dwarf variety at the 

 right. In the line immediately below is the first (Fi) generation, all plants of 

 which are tall and thus like the tall parent, and each of which upon being self- 

 fertilized produced a progeny (F-z generation) consisting of tall and dwarf 

 plants in the ratio of 3 : 1, as shown in the third line. As shown in the lower 

 line (F s generation), the dwarfs and one-third of tails of the Fz generation bred 

 true, that is, they produced progeny like themselves, while two-thirds of the 

 tall ones produced a progeny consisting of tall and dwarf plants in the ratio 

 of 3 : 1. 



