, 



HEREDITY IN WILLOWS 

 (After Wiesner) 



A, a broad-leaved variety, the one parent. 

 C, a narrow-leaved variety, the other parent. 



B, the hybrid offspring, intermediate between the two. This has an appear- 

 ance of blending, but it may be a case of imperfect dominance, as in the 

 Andalusian fowls. Or it may be that the shape of the leaf depends upon a 

 number of Mendelian unit characters which are not linked together but pro- 

 duce an appearance of blending by their fortuitous distribution in the offspring. 

 If some come from the one parent and some from the other they may neutralise 

 one another, with an apparent " blend " as the result. 



" 



MENDEI. S LAW ILLUSTKATKD IN I'l \- 



A. Pod of a yellow-seeded pea. the one parent (dominant as 

 to seed-colour). 



B. Pod of a green-seeded pea, the other parent (recessive as 

 to seed -colour). 



C. Pod of the hybrid offspring (the first filial generation), 

 with only yellow seeds. Yellow-seededness is dominant and 

 green-seededness recessive. 



D. The next generation (the second filial generation) shows 

 the occurrence of both yellow seeds (left light) and green seeds 

 (shaded dark). 



