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illustrated, supplies us with a sufficient and intelligible cause, 

 both for the general distribution of this boreal flora through- 

 out our island, and also, to some extent, for its more special 

 distribution amongst our different mountain regions. No other 

 theory which has yet been propounded upon the subject is so 

 probable in itself, or recommended by such valid reasons ; while 

 everything that we know of the phenomena of this geological 

 epoch, and the peculiarities of this phytological distribution, serve 

 but to give even additional confirmation to what it possessed in 

 the days of Forbes. Nor does it in any way invalidate its strong 

 claims to our acceptance to find that some species, not natives 

 of the Scandinavian Mountains but of the Alps, are found 

 sparingly in one or two localities in the British ranges. For it 

 was only to be expected that these should, in return for species 

 received from the icy north, give back to our latitudes some few 

 of their own on the retirement of the glacial ocean. And the 

 only other consideration which at first sight seems to militate 

 against it, is capable of an easy and satisfactory explanation. 

 This is the fact of numerous lowland plants being present amongst 

 these alpine ones, and in some few cases attaining an almost 

 equal elevation. These, however, are not contemporaneous with 

 their sub-arctic sisters, but belong to a later geological epoch. 

 They were introduced after the glacial sea had disappeared, and 

 the uplands and lowlands emerged from its bosom, after the 

 islands had been elevated into mountains and connected together 

 by dry land, after the climate had become greatly changed, 

 though the glaciers still lingered in the higher corries, when 

 Britain was joined to Germany and Ireland to Britain, and 

 everything was suitable for another type of vegetation from a 

 more southerly clime, obtaining a firm footing in the country, 

 and gradually, in the course of long ages, as the temperature 

 and natural features of the country became as they now are, 

 spreading itself from the lowlands to the uplands, and 



