FLORA OF THE DRIFT. 207 



pine (Pinus ccmbra) liavo boon found; and at Bovcy Tracey, in 

 Devonshire, a white clay covering a great Miocene deposit of 

 lignite contains willow leaves and well-preserved leaves of the 

 dwarf birch (Betula nana, Linn.*) . The latter is not now found 

 in England ; but it grows upon the mountains of Scotland. It 

 is widely distributed in the Arctic zone, and occurs also in 

 Switzerland, but only in the peat-bogs of the Jura and of 

 Einsicdeln. 



The two last-mentioned plants, the dwarf birch and the Sibe- 

 rian pine, at least furnish an indication that Alpine and northern 

 plants have lived in lower and more southerly situations. In 

 1872, near Schwerzenbach in the Canton of Zurich, an Alpine 

 flora was found, in drift loam, comprising the Betula nana, 

 Salix retusa, S. reticulata, S. polaris, Polygonum viviparum, and 

 Dry as octopetala. A remarkable phenomenon is noticed in the 

 existing Swiss flora, which can only be satisfactorily explained 

 on the supposition that the Alpine flora once extended down 

 into the plains. This is the occurrence of colonies of Alpine 

 plants on the hills and in the peat-mosses of the plains of Swit- 

 zerland. It is not surprising that the glaciers and rivulets 

 going down into the valleys should have been accompanied by 

 many Alpine plants which remain isolated on their borders ; 

 but colonies of the vegetable inhabitants of the mountains are 

 met with on the hills of the low country, far from the mountain- 

 streams and from the Alps. They appear then like lost children 

 of the Alps, surrounded only by plants belonging to the plain. 

 Leaving out of account the species accidentally floated down, 

 the Canton of Zurich comprises 123 mountain-plants, 55 of 

 which have their home in the Alps, and may therefore be cha- 

 racterized as Alpine plants ; and yet the highest point in the 

 Canton scarcely attains an elevation of 4000 feet above the sea. 

 It is true that the chain of the Hornli is not far from the high 

 mountains, yet is it separated from them by the broad valley of 

 the Toggenburg. Nor are the Albis range and the Hohe- 

 Rhoncii directly connected with the Alpine system ; and the 

 Uetlibcrg, the Irchel, and the Lagern are very remote from it. 



* Prof. Ileer lias figured this in liis memoir " On the Fossil Flora of Bovev- 

 Trticoy,'' in tho Phil. Trans*. 1802, pi. Ixxi. 



