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, 
_L_L 
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 of contrasting characters 
