CHAPTER XX 



THE ORIGIN OF OUR BRITISH FLORA 



What is known of the European flora before the great 

 series of Ice Ages had entirely altered its character is in 

 a way satisfactory and yet a little bewildering. 



In Eocene, Miocene, and Pliocene times in France, a 

 very strange mixture of plants have been recognised. In 

 the same stratum there may occur two species which are 

 no\v separated by, for instance, the entire width of Europe 

 and Asia, or what is much more difficult to understand, 

 two forms which we now consider characteristic of 

 temperate and subtropical climates respectively, and yet 

 which had, in the Ardeche, been involved in the same 

 volcanic eruption and whose fossil leaves are found side 

 by side.^ 



It is supposed that these French deposits show a 

 distinct change of climate. In the Upper Pliocene they 

 seem to suggest that the Great Ice Age is already looming 

 in the distant future. But on the whole, M. Laurent 

 refers to the fertile valleys of the Caucasus as explaining 

 this mixture of different vegetations in the flora of 

 Cordagne and Charay at that very ancient date. 



When the glaciers invaded Northern France and 

 covered the whole of North-western Europe, from 

 Norfolk upwards, in a winding sheet of snow, the 

 ancient European flora was of course in large part 

 destroyed. 



It seems that even before those days many species and 

 perhaps the present kind of temperate deciduous wood- 

 lands were to be found on the Pyrenees, Alps, and 



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