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THE AMERICAN NATURALIST [Vol. XLIX 



cate any sort of hybridization. For example, Bat ibid a 

 columnifera presents many variations parallel with those 

 of Helianthus, in localities where it is the only species of 

 its genus. 



4. We are led, then, to think of the annual sunflowers as 

 plants representing a certain complex of potentialities or 

 genes (of which we may hope at length to make a reason- 

 ably complete catalogue), offering these in different com- 

 binations at different times, usually failing to register 

 any permanent advance, but once in a long while reaching 

 a new position of stability, suited to a particular en- 

 vironment. These positions of stability represent what 

 we call the species. As with the dahlia, the horticulturist 

 may expect to be able to produce many interesting varie- 

 ties by selecting and saving the various possible combina- 

 tions, but analysis shows that the genes going into these 

 are the old ones, the effects of which may be seen from 

 time to time even in wild plants. 



The perennial sunflowers appear to offer a more com- 

 plex problem. Mr. S. Alexander has found hundreds of 

 what are considered " elementary species " in Michigan. 

 He has been good enough to send me a large number of 

 these, and I can testify that they are appreciably differ- 

 ent; yet they seem to represent recombinations of old 

 characters, already known to exist in the species of the 

 manuals. Some would dismiss them, along with the mul- 

 titudes of Crataegus, as hybrids ; but it does not seem justi- 

 fiable to assume hybridization without better evidence. 

 We have sufficient proof, I think, that all sorts of new 

 combinations of characters may arise within a type, with- 

 out hybridization. 



Undoubtedly new determiners are formed (how, we 

 need not here speculate) from time to time, but the oc- 

 currence must be so rare and so difficult to demonstrate 

 that we can hardly hope to obtain satisfactory evidence 

 concerning it. 



