SOME ALPINE CLIMIiERS. 31$ 



XXXVI. 



SOME ALPINE CUMBERS. 



Ox the very summit of the moor here, among the mossy 

 clefts of the weathered granite, a few straggh'ng tufts of 

 northern rockcress still manage to keep good their 

 footing on an area not wider in every direction than the 

 circle described by a radius of some four or five hundred 

 yards from the central boulder on which I am sitting. 

 Small as is the patch of ground over which they thus 

 extend, they can doubtless boast a very considerable 

 prehistoric antiquity ; for there is every reason to believe 

 that they and their ancestors have struggled on here in 

 lonely isolation ever since the end of the great glacial 

 era. Nothing adds so much to the romance of natural 

 history as the fixed habit of regarding every separate 

 colony of plants or animals as a tribe or community, 

 necessarily restricted to intermarriage with other members 

 of the same group in the same place ; it almost compels 

 one to ask oneself in each case, how did they first get 

 here, and how did they come to be permanently severed 

 from the main body of their species elsewhere ? Now 

 northern rockcress is by origin a sub-arctic plant, 

 spreading along all the higher ranges of Scandinavia, 

 Russia, and Siberia, with a {q.\\ isolated outliers among 

 the snowy mountains of southern Europe. Here in 



