42 THEORY OF EVOLUTION 



garden plant called four o'clock (Mirabilis jal- 

 apa) with red flowers is crossed to one having 

 white flowers, the offspring are pink (fig. 13). 

 The hybrid, then, is intermediate in the color of 



PARENTS 



FIG. 13. Diagram illustrating a cross between a red (dark) 

 and a white variety of four o'clock (Mirabilis jalapa). 



its flowers between the two parents. If these 

 hybrids are inbred the offspring are white, pink 

 and red, in the proportion of 1:2:1. All of 

 these had the same ancestry, yet they are of 

 three different kinds. If we did not know their 



