European Vegetation. 129 



intelligible explanation. The Peak of Teneriffe, which rises 

 to a greater height and is much nearer to Europe, contains 

 no such Alpine flora, neither do the mountains of Bourbon 

 and Mauritius. The case of the volcanic peaks of Java is 

 therefore somewhat exceptional, but there are several analo- 

 gous, if not exactly parallel cases, that wall enable us better 

 to understand in what way the phenomena may possibly have 

 been brought about. The higher peaks of the Alps, and even 

 of the Pyrenees, contain a number of plants absolutely iden- 

 tical with those of Lapland, but nowhere found in the inter- 

 vening plains. On the summit of the White Mountains, in 

 the United States, every plant is identical with sj^ecies grow- 

 ing in Labrador. In these cases all ordinary means of trans- 

 port fail. Most of the j^lants have heavy seeds, which could 

 not possibly be carried such immense distances by the wind ; 

 and the agency of birds in so efiectually stocking these Al- 

 pine heights is equally out of the question. The difficulty 

 was so great that some naturalists were driven to believe 

 that these species were all sej^arately created twice over on 

 these distant peaks. The determination of a recent glacial 

 epoch, however, soon offered a much more satisfactory solu- 

 tion, and one that is now universally accej^ted by men of 

 science. At this period, when the mountains of Wales were 

 full of glaciers, and the mountainous parts of Central Europe, 

 and much of America north of the great lakes, were cover- 

 ■ ed with snow and ice, and had a climate resembling that of 

 Labrador and Greenland at the present day, an Arctic flora 

 covered all these regions. As this epoch of cold passed 

 away, and the snowy mantle of the country, with the glaciers 

 that descended from every mountain summit, receded up 

 their slopes and toward the North Pole, the plants receded 

 also, always clinging as now to the margins of the perpetual 

 snow-line. Thus it is that the same species are now found 

 on the summits of the mountains of temperate Europe and 

 America, and in the barren north-polar regions. 



But there is another set of facts, which help us on another 

 step toward the case of the Javanese mountain flora. On the 

 higher slopes of the Himalaya, on the tops of the mountains 

 of Central India and of Abyssinia, a number of plants occur 

 which, though not identical with those of European mount- 



I 



