440 X. GENERAL REMARKS. 



without spreading more widely, or without visibly con- 

 tracting their areas, where left undisturbed by man, the 

 great intermeddling agent of nature. Not unlikely, how- 

 ever, this non- changeability in the limited localities of 

 some species is more seeming than real, the deceptive 

 inference from a brief and imperfect observation. 



The larger number of species may be said to evince a 

 tendency towards continuity of diffusion, interrupted or 

 arrested in such places, and under such conditions, as 

 may fauiy be considered more or less satisfactorily to 

 account for the facts observed. For example, on finding 

 various species upon the higher mountains of Scotland, 

 which are absent from the low and comparatively^ warm 

 plains and coasts of Britain to the southward of those 

 mountains, and which are known again on the plains and 

 shores of arctic countries, — the inference in this case is 

 obvious and irresistible, that the cold and humid climate 

 of the Scottish mountains is one of the present related 

 conditions, assisting to preserve and keep the plants 

 there ; although not sufficing by itself to exijlain how 

 they originally got to that locality. 



Again, Primula scotica is found in some few places 

 near or along the northern coasts of Scotland, but not 

 spreading to similar situations more southward, nor 

 rising to the higher mountains. Though sufficiently 

 puzzling still, this very restristed area in Scotland was 

 yet more inexplicable so long as the same sjjecies was 

 believed to occur in no other country. Since it has been 

 ascertained to occur also on the mountains of Scandi- 

 navia, a plausible conjecture can at any rate now be 

 made, that it has emigrated from those mountains to the 

 moorland coasts of Scotland, — and that some peculiar 

 adaptation to soil or climate, or possibly the want of suffi- 

 cient lapse of time, may have prevented the extension of 



