THE MENDELIAX PRINCIPLES OF HEREDITY 79 



The first and the last will breed true, if self-fertilized, 

 because they are pure races, while the black-and-whites 

 will give once again, if inbred, the proportions 1:2: 1. 

 A better illustration of Mendel's principles is shown 

 in the case of the white and red Mirabilis jalapa de- 

 scribed by Correns. This case is illustrated in Fig. 44, 



FIG. 44. Cross between white and red races of Mirabilis Jalapa, giving 

 a pink hybrid in FI which when inbred gives, in F 2 , 1 white, 2 pink, 1 red. 



in which the red flower is represented in black and the 

 pink is in gray. The hybrid, F^ out of white by red, 

 has pink flowers, i.e. it is intermediate in color. When 

 these pink flowers are self-fertilized they produce 

 1 white, 2 pink, and 1 red-flowered plant again. The 

 history of the germ-cells is shown in Fig. 45. The germ- 



st 



