298 Retrograde Varieties 



that both are present, and in nearly equal num- 

 bers ; one-half of the grains remaining smooth, 

 and the other half becoming wrinkled. 



The corresponding experiment could be made 

 with plants of a pure sugar-race by pollination 

 with hybrid pollen. The spikes would show ex- 

 actly the same mixture as in the above case, but 

 now this may be considered as conclusive proof 

 that half the pollen-grains represent the quality 

 of one parent and the other half the quality of 

 the other. 



Another corollary of Mendel's law is the fol- 

 lowing. In each generation two groups return 

 to purity, and one-half remains hybrid. These 

 last will repeat the same phenomenon of split- 

 ting in their progeny, and it is easily seen 

 that the same rule will hold good for all succeed- 

 ing generations. According to Mendel's prin- 

 ciple, in each year there is a new hybridization, 

 differing in no respect from the first and 

 original one. If the hybrids only are propa- 

 gated, each year will show one-fourth of the 

 offspring returning to the specific character, 

 one-fourth assuming the type of the variety and 

 one-half remaining hybrid. I have tested this 

 with a hybrid between the ordinary nightshade 

 with black berries, and its variety, Solanum 

 nigrum chlorocarpum, with pale yellow fruits. 

 Eight generations of the hybrids were culti- 



