MENDELISM 15 



to all appearance quite similar, are yet differently constituted, 

 for a is formed of two dominant germ-cells, whereas in b the 

 pollen grain alone is dominant, and in c the ovule only is 

 dominant. 



a is a "pure dominant"; 



b and c are " impure dominants " ; 



d is a "pure recessive." 



Thus in the Fij generation we get, not three dominants 

 to one recessive, but one pure dominant, two impure 

 dominants, and one pure recessive. We must therefore 

 amend the diagram on p. 1 1 thus — 



D x R 

 D[R] = Fj 



DD D[R] D[R] RR = Fij 



The former diagram shows their appearance — this shows 

 their Constihition. 



This is the usual result of the self-fertilization of 

 hybrids of any contrasted pairs, and thus 



in the Fij generation we get 3 tails to 1 dwarf, 



3 coloured to 1 white, 



3 smooth seeds to 1 wrinkled, 



3 yellow seeds to 1 green. 



When breeding is further continued we find that the 

 pure dominant (DD) of Fij always breeds true, and pro- 

 duces — e. g. in case of stature, none but tall plants ; the 

 recessive (RR) produces none but dwarf plants ; and the 

 impure dominants (D[R]) produce the same kinds of off- 

 spring, and in the same proportions that the Fj generation 

 produced, viz. — 



1 DD, 2 D[R], and 1 RR. 



