DIFFICULTIES AS TO THE THEORY 305 



from some of the ancient Arctic plants, which became 

 established in the plains. Both in Europe and North 

 America, as the glaciation decreased, some of the 

 ancient Arctic, as well as the ancient Alpine species, 

 ascended the mountains, and gave rise eventually to 

 the modern Alpine floras of these continents. 



Such is the bare outline of the theory which has 

 been advanced to account for the origin of the Alpine 

 flora. It is quite impossible to discuss the evidence 

 for, or against, it here. At any rate, it will explain 

 the facts of the present-day distribution of Swiss 

 Alpine plants, which we have already enumerated. It 

 will explain why some of the Alpines of Europe and 

 North America are identical, while the Lowland floras 

 of these regions are very dissimilar. It will explain 

 the isolated seclusion of Alpines on the various 

 detached mountain chains of Europe and elsewhere 

 without any appeal to the theory of multiple centres 

 of origin of species. It furnishes a reasonable historic 

 connection between the facts of the past and the 

 present. 



At the same time, it must be pointed out that 

 difficulties exist, either as to the theory as a whole, 

 or as to some of its essential components, which have 

 led such authorities as Dr Christ and the late John 

 Ball to dissent from it. The relationship between 

 the present Alpine and Arctic floras is the chief 

 stumbling block. A large number, in fact the majority, 

 of Swiss Alpines do not occur in the Arctic. It has 

 been urged that Central Asia was the original home 



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