44 



Plant Genetics 



Mirabilis Jalapa, the common four-o'clock. Correns 

 crossed red and white varieties, and all the hybrid 

 progeny had rose pink flowers. This was a color blend, 

 distinctly intermediate between the colors of the two 

 parents. The Fi generation, therefore, seemed to con- 

 tradict Mendel's law in that one color character was 

 not completely dominant over the other. The real situa- 

 tion, however, appeared in the Fj generation obtained by 



Fig. 8. — Diagram illustrating blending inheritance, discovered 

 by Correns in Mirabilis Jalapa. 



inbreeding individuals of the Fi generation which showed 

 the blend. By inbreeding the pink hybrids Correns 

 obtained the perfect 1:2:1 ratio, that is, i red like one 

 grandparent, 2 pink Uke the hybrid parent, and i white 

 like the other grandparent. Segregation was evidently 

 taking place, the only unusual thing being the appear- 

 ance of the Fi individuals, and that was explained im- 

 mediately as failure of dominance (see fig. 8). 



