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, and 

 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 blackberries, and its variety, Solanum 

 nigrum chlorocarpum, with pale yellow fruits. 

 Eight generations of the hybrids were culti- 



