A Motmtazn Tulip. 189 



northern rock-cress, the Arctic whitlow-grass, the 

 Alpine pearlwort, the Scottish asphodel, the mossy 

 cyphel, the mountain lady's mantle, the purple saxi- 

 frage, and the red bearberry. Altogether, we have 

 still more than two hundred such Alpine or Arctic 

 plants, stranded among our uplands or in the extreme 

 north of Scotland, and probably separated for many 

 thousand years from the main body of their kind in 

 the Arctic Circle or the snowy mountains of central 

 Europe. 



Our pretty little Lloydia here is far rarer in Britain 

 than these low mountain kinds ; for it has died out 

 utterly even in Scotland itself, and now survives no- 

 where with us except on these solitary Welsh summits. 

 Such cases are frequent enough in Britain ; for while 

 the moderate mountainous or Arctic species still go 

 on thriving among the straths and corries, the coldest 

 kinds of all have often been pushed upward and ever 

 upward by the advancing tide of southern flowers till 

 they are left at last only on a few isolated mountain 

 tops, where many of them are even now in course of 

 slowly disappearing before the steady advance of the 

 southern types. For example, there is a certain pretty 

 kind of heath, confined to northern or Arctic hillsides, 

 which till lately lingered on in Britain only on the one 

 mountain known as the Sow of Atholc in Perthshire ; 



