198 Retrograde Varieties 



improvement as may be obtained with a mini- 

 mmn of cost, and this mostly implies a culture in 

 the same part of the nursery with older varie- 

 ties of the same species. Three, four or five 

 years are required to purify the novelty, and 

 as this same length of time is also required to 

 produce sufficient quantities of seed for 

 commercial purposes, there is no strong 

 desire to shorten the period of selection and 

 fixation. I had occasion to see this process go- 

 ing on with sundry novelties at Erfurt in 

 Germany. Among them a chamois-colored va- 

 riety of the common stock, a bluish Clarkia 

 elegans and a curiously colored opium-poppy 

 may be mentioned. In some cases the cross- 

 fertilization is so overwhelming, that in the 

 next generation the novelty seems entirely to 

 have disappeared. 



The examples given may suffice to convey a 

 general idea of the phenomenon, ordinarily 

 called ata\dsm by gardeners, and considered 

 mostly to be the effect of some innate tendency 

 to revert to the ancestral form. It is on this 

 conception that the almost universal belief 

 rests, that varieties are distinguished, as such, 

 from species by their inconstancy. Now I do 

 not deny the phenomenon itself. The impurity 

 of seeds and cultures is so general and so mani- 

 fest, and may so easily be tested by every one 



