22 LINKS WITH THE PAST [ch. 



species. The Scandinavian flora, as Sir Joseph 

 Hooker says in his well-known paper on the 'Out- 

 lines of the Distribution of Arctic plants,' ' not only 

 girdles the globe in the Arctic Circle, and dominates 

 over all others in the North Temperate Zone of the 

 Old World, but intrudes conspicuously into every 

 other temperate flora, whether in the northern or 

 southern hemisphere, or on the Alps of tropical 

 countries '(17). The vicAV generally held is that during 

 the Glacial period this Arctic flora was driven 

 South, and aided by land-bridges, which were after- 

 wards submerged, many of the northern migrants 

 found a more congenial home in Britain. It is how- 

 ever by no means improbable that this conclusion 

 may have to be considerably modified. Mr and Mrs 

 Reid, as the result of their careful analysis of the 

 Pre-Glacial Flora of Britain, express the opinion that 

 Hhe pre-glacial plants suggest climatic conditions 

 almost identical with those now existing, though 

 slightly warmer' (27, 2). It is noteworthy that the 

 list of plants given in their paper does not include 

 any typical Arctic species. The occurrence on the 

 mountains of Scotland and elsewhere of such plants as 

 Silene acaulis, Dry as octopetaJa, Saxlfraga oppositi- 

 folia and other Saxifrages, Ruhns chamaemorus (the 

 Cloudberry), and the dwarf Birch illustrate the Arctic- 

 Alpine element in our flora. 



The opinion is held by many Swiss botanists that 



