554 



STRUCTURE AND LIFE HISTORIES 



by his experiments was that, in such a cross, all the seeds 

 of the hybrid plants are smooth. The inheritance was 

 "smooth" and "wrinkled," but the expression was of 

 only one type — smooth. A character thus expressed, 



Fig. 407. — Mendelian segregation in the edible pea {Pisum sativum). 

 Full explanation in the text. (Cf., Fig. 408.) 



to the exclusion of another, in the first filial (Fi) genera- 

 tion Mendel called dominant, and the phenomenon he 

 called dominance; the other character is recessive. From 

 such observations Mendel formulated the law of domi- 

 nance, as follows: When pairs oj contrasting characters 



