12 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



to warrant our confidence in urging the wide cultivation of these 

 and similar species in European countries, particularly in the 

 north. 



From this hasty analysis of Dr. Gray's elaboration of his 

 favourite genus it is evident that a considerable number of 

 species are promising subjects for cultivation. They evince an 

 immediate response to better surroundings, except in the case of 

 some of those which prefer a sterile soil. 



No one can examine the species of this genus as they appear 

 in a ramble through any of the eastern or of the middle portion 

 of what we used to call the West in America without being 

 impressed by the immense number of intermediate forms and of 

 the wide variation in the well-marked species. They display 

 such differences as to assure any horticulturist of a speedy 

 reward from selection alone. But when we add to this the fact 

 that so many of them hybridise spontaneously, giving us 

 stronger plants, although perhaps relatively infertile, it is easy to 

 understand how wide is the field from which a skilful cultivator 

 can choose the material for his work. 



Lastly, even a cursory examination of the species shows that 

 geographical representatives are everywhere found in this poly- 

 morphous genus. A given species will vary, we will say, in two 

 directions. On one side of the range of this variation will be 

 found a species connected by intermediate forms, and this may 

 serve as the type of extreme divergence on that side and limit. 

 On the other side will be found other forms, and these may be 

 gathered around a type which marks the limit in that direction. 

 It is really curious to see how often a species is bounded by 

 morphological limits which are nearly coincident with geo- 

 graphical ones. The bearings of this on the practical question 

 which this paper has undertaken to present are plain : a study 

 of these geographical relations will in most cases indicate what 

 we can expect for our gardens and point out a method of treat- 

 ment there. With the kindred subject suggested by such a geo- 

 graphical study, namely, as to the probable point of origin of the 

 American Asters, the present paper cannot deal. It is reserved 

 for another time and place. 



