140 ORIGIN OF LIFE IN AMERICA 



eastern States as it is at present. A more pronounced 

 climatic differentiation between the two parts of North 

 America supervened, he thinks, in later Tertiary times, and 

 while many of the species became extinct in the western 

 States owing to the gradually increasing dryness of the 

 climate, new forms better adapted to the altered conditions 

 arose. Hence certain types of plants are represented in the 

 western States by many, and in the eastern by few species. 



It is evident that Professor Engler* favours the view that 

 the western States were once much more nearly related in 

 their flora to eastern and southern Asia than the eastern 

 States, and that the present similarity between the latter 

 regions has arisen as a secondary character. Professor 

 Engler, moreover, believes and in this respect my views 

 differ from his that Japan, western and eastern America 

 were connected with one another in the north during the 

 Tertiary Era and probably even in Cretaceous times, forming 

 three great peninsulas of land joined at their northern bases. 

 At any rate, the distribution of plants in America seems to 

 offer a certain amount of support to the view suggested, that 

 the relationship of the east American and east Asiatic faunas 

 is due to the recent geological changes in south-western North 

 America having obliterated the more striking features of 

 resemblance between the latter and eastern Asia. 



In connection with the character of the north eastern flora 

 just referred to, I might offer a few remarks on the subject 

 of the supposed former eastward extension of the land. This 

 subject was discussed towards the end of the second chapter. 

 I then maintained that, although the north-eastern States 

 had been under water in Pleistocene times, unsubmerged 

 land existed to the eastward quite close to, and including 

 portions of the present shore-line. 



Probably one of the best recognised and most characteristic 

 elements of the eastern North American floras, as Mr. Hollick 

 remarks, is the one generally known as the " Pine-barren 

 flora," which is such a prominent feature throughout the 

 eastern and southern parts of New Jersey and southward. 



* Engler, A., " Entwicklungsgeschichte d. Florengebiete," I., pp. 22 

 37. 



