28 



TYPES OF MENDELIAN HEREDITY 



the factor for white both affect the plant in which they 

 occur. In this agd in similar cases the Fo ratio of 

 1 :2 : 1 is obtained, because it is possible to distinguish 

 the pure red and the pure white from the heterozygous 

 plants. 



Fig. 14. — Diagram to illustrate the cross between a red and a white 

 flowered Mirabilis jalapa (4 o'clock), which produces a pink, intermediate 

 heterozygote. 



The Andalusian fowl is a similar case. When 

 certain races of black are bred to certain races or 

 kinds of ^Svhite" the hybrid is slate ^'blue" in color. 

 These blue birds, called Andalusians, when inbred, 

 give one black to two blue to one white. Blue is 



