THE MENDELIAN 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, 



PARENTS 



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

 a pink hybrid in F\ which when inbred gives, in F-i, 1 white, 2 pink, 1 red. 



in which the red flower is represented in black and the 

 pink is in gray. The hybrid, Fi, 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- 



