INTRODUCTORY EXPLANATIONS. 33 



prevent confusion with subordinate divisions, it may be well 

 to say, in the first instance, Agrarian Region and Arctic 

 Region. 



In the spontaneous vegetation of Britain, we can find no 

 character equally obvious and general with that afforded by 

 the cultivation of gi-ain. The interests of mankind are so 

 intimately connected with the production of corn, that we 

 shall everywhere find cultivated fields as far up the valleys 

 and acclivities of the momitains, as their climate will allow. 

 No doubt we may see many spots where the natm-e of the 

 soil or sm-face, rather than the climate, forbids success in 

 cultivation. But a correct observer can scarcely be misled 

 in such instances, since he wiU usually find cultivation suf- 

 ficiently near these spots, to show that it has not been pre- 

 vented by inferiority of climate. Moreover, nature will 

 afford us a second test of the Agrarian region, by the pre- 

 sence of a very common and conspicuous fern, the Pteris 

 aquilina. This fern is distributed throughout the region, 

 and fi'om one extremity of our island to the other ; its upper 

 limit usually running nearly uniform with the climatic limit 

 of corn cultivation; so that the two characters in con- 

 nexion form a satisfactory test of the region. The plough 

 is soon fatal to the Pteris, nor can it long resist the annual 

 attack of the scythe in early summer ; but we require its 

 presence, as a chaiacter, only in those spots which remain 

 uninvaded by scythe or ploughshare ; and in such spots we 

 seldom seek it in vain, until arriving about the line where 

 climate itself aiTests the ascent of agricultm-e. 



Among the Highland mountains, the highest spot at 

 which the cultivation of grain has been observed by the 

 writer of these pages, was at the outlet of Loch Callater, 

 estimated to be 1,600 feet above the sea. Potatoes can 

 scarcely be grown in Drumochter Pass, which is calculated 

 at 1 ,530 feet above the sea, and is much more .shadowed by 



