1915] 



WILLE FLORA OF NORWAY 75 



ous age with a colder climate, but I do not think we need 

 have recourse to such an explanation. In all the steep-sided 

 valleys, typical mountain plants spread downward along 

 streams and rivers, and often appear far below their real 

 habitat. Whether they will remain there depends only upon 

 their ability to compete with lowland plants and to withstand 

 the night frosts in the spring after the snow has melted. 



I assume, therefore, that the occurrence of the above- 

 mentioned mountain plants in the lowlands is due to a chance 

 carrying of seed to places that were favorable to the welfare 

 of the species, e.g., limestone at Langesund and Varaldso for 

 Dry as octopetala, a peat-bog for Betula nana, and so forth. 



The Immigration of the Norwegian Flora 



Geologists have long been agreed that Scandinavia and 

 great parts of adjacent lands have once been covered with 

 one entire ice-cap, as the interior of Greenland is at the 

 present time. By degrees the view obtained that there have 

 really been two such glacial epochs, separated by an inter- 

 mediate warm period, in which the conditions probably more 

 or less resembled those of the present day. 



During the first, called the Great Glacial Epoch, the ice- 

 cap extended as far as central Germany, over almost the 

 whole of England, over the whole of Finland, and over a 

 great part of northern Russia. It follows that under such 

 conditions, all, or almost all, vegetation must have disap- 

 peared from the Scandinavian peninsula, from Norway and 

 Sweden. I am inclined to believe that in places in Norway, 

 the tops of high mountains rose above the ice-covering, and 

 that a very few species of plants may have survived there; 

 but this is a matter of no interest in the question upon which 

 I shall now endeavor to throw light, namely, the immigration 

 of the flora of Norway after the Last Glacial Period. 



This was of considerably smaller extent. On the south 

 the ice reached only as far as Mecklenburg, and the ice- 

 boundary then ran obliquely northward up through Jutland 

 in Denmark, of which, therefore, only a part was entirely 

 covered with ice. There can be no doubt that the whole of 



