6 



THE THEORY OF THE GENE 



In passing it is important to note two facts. The red 

 and the white F, individuals are expected to breed true, 

 because they contain the elements for red, or for white, 



Pi 



Fig. 5. 

 A cross between a red-flowered four-o'clock (Mirabilis Jalapa) 

 and a white-flowered four-o'clock, giving pink in F 1; and one red, 

 two pink, one white in F 2 . 



twice present (Fig. 6), but the pink F 2 individuals should 

 not breed true, since they are like the first hybrid genera- 

 tion, and contain one red and one white element (Fig. 6). 

 All this turns out to be true when these plants are tested. 



