10 The Scottish Flora. 



our own scientific leaders do not trouble to translate and make 

 accessible for us even a minute portion of the valuable foreign 

 work annually produced. So that it is a very difficult matter to 

 give at all a complete account of the best foreign opinion on the 

 history of the flora of Europe. 



When the glaciers and ice sheets of the fourth and greatest 

 Ice Age finally abandoned Northern Europe, the country was 

 soon inhabited by what is known as the Dryas Flora. It was a 

 dwarf, starved, spotted sort of vegetation,' consisting for the most 

 part of miserable little willows and tiny birches. Some of them 

 are still with us ; but others have departed for the frozen north, 

 and are no longer Scotch citizens. After an interval of time, 

 longer or shorter, according to the locality and exposure, well- 

 grown thickets and woods of our common birch with alder, hazel, 

 and other plants, dispossessed those scrubby little Arctic alpines. 

 Willows, populus tremula, and juniper came with the birch forest. 

 It was still a cold climate, with an average July temperature of 

 9 deg. C, and in August 7 deg. or 8 deg. C. Then came the 

 Scotch pine, which formed regular forests, and brought many 

 other plants along with it. This reigned as the dominant vegeta- 

 tion in Scotland for thousands of years. The June temperature 

 was 9 deg. C. ; July, 12 deg. C. ; and August, 10 deg. C. But 

 after a long interval oak forest dispossessed the pines, and was 

 accompanied by many more of our common woodland flowers. 

 The temperatures were as follows: — June, 14 deg. C. ; July, 1^ 

 deg. C. ; and August, 14-15 deg. C. 



The Continental evidence seems quite clear as to these suc- 

 cessive invasions, at least for Norway, Sweden, Denmark, 

 Schleswig-Holstein, North Germany, and Russia. Moreover, if 

 one were to start, preferably by aeroplane, from Dumfries and 

 travel to the Arctic regions, one would pass over, in succession, 

 all those vegetations — oak, conifer, birch, and Arctic alpine flora. 

 Then again, in ascending, say, the Alps, something very similar 

 occurs. There is a lower deciduous forest, a Highland conifer 

 forest. Above this is sometimes a zone of birches, and near the 

 snow line are many of those very Arctic alpines which form the 

 Dryas flora. So that the present facts of distribution supplement 

 very clearly the above series of vegetation forms. Everything is 

 just as it should be. 



