chap, vii.] THE GLACIAL EPOCH. 137 



those of European mountains, belong to the same genera, 

 and are said by botanists to represent them ; and most 

 of these could not exist in the warm intervening plains. 

 Mr. Darwin believes that this class of facts can be 

 explained in the same way ; for, during the greatest severity 

 of the glacial epoch, temperate forms of plants will have 

 extended to the confines of the tropics, and on its de- 

 parture, will have retreated up these southern mountains, 

 as well as northward to the plains and hills of Europe. 

 But in this case, the time elapsed, and the great change 

 of conditions, have allowed many of these plants to become 

 so modified that we now consider them to be distinct 

 species. A variety of other facts of a similar nature, have 

 led him to believe that the depression of temperature was 

 at one time sufficient to allow a few north-temperate 

 plants to cross the Equator (by the most elevated routes) 

 and to reach the Antarctic regions, where they are now 

 found. The evidence on which this belief rests, will be 

 found in the latter part of Chapter II. of the " Origin 

 of Species ; " and, accepting it for the present as an 

 hypothesis, it enables us to account for the presence of 

 a flora of European type on the volcanoes of Java. 



It will, however, naturally be objected that there is 

 a wide expanse of sea between Java and the continent, 

 which would have effectually prevented the immigration 

 of temperate forms of plants during the glacial epoch. 



