452 ALPINE AND ARCTIC PLANTS 



American, but S. uva-ursi seems to be confined to America. 

 Rubus triflorus, the dwarf raspberry, and R. chamcemorus, the 

 cloud berry, climb about equally high on Mount Washington ; 

 but the former is exclusively American, and ranges pretty far 

 southward, while the latter extends no farther south than the 

 northern coast of Maine, and is distributed all around the 

 Arctic regions of the Old and New Worlds. It is to be 

 observed, however, that the former can thrive on rich and 

 calcareous soils, while the latter loves those that are barren 

 and granitic ; but it is nevertheless probable that R. triflorus 

 belongs to a later and more local flora. Similar reasons would 

 induce the belief that the American dwarf cornel or pigeon- 

 berry (Cornus Canadensis), whose distribution is solely Ameri- 

 can, and not properly Arctic, is of later origin than the C. 

 Suecica? which occurs in northern America locally, and is ex- 

 tensively distributed in northern Europe. 



I can but glance at such points as these ; but they raise great 

 questions which are to be worked out, not merely by the patient 

 collection of facts, but by a style of scientific thought very 

 much above those which, on the one hand, escape such prob- 

 lems by the supposition of multiplied centres of creation, or 

 on the other, render their solution worthless by confounding 

 races due to external disturbing causes with species originally 

 distinct. Difficulties of various kinds are easily evaded by 

 either of these extreme views ; but with the fact before him of 

 specific diversity and its manifestly long continuance, on the 

 one hand, and the remarkable migrations of some species on 

 the other, the true naturalist must be content to work out the 

 problems presented to him with the data afforded by the actual 

 observation of nature, following carefully the threads of guid- 



1 I have found C. Suecica growing along with C. Canadensis in shaded 

 and northern exposures on the south side of the St. Lawrence, near Ca- 

 conna and Metis. Its seeds may have been brought over from Labrador 

 by migratory birds. 



