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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. 
Tn 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. 
