y 



72 ^' W. Chaney 



and Eocene floras of Asia than between those of the same series 

 in western North America. This may be accounted for by the 

 comparative remoteness of the Asiatic floras from the Atlantic 

 Ocean and its cUmatic effects; whereas changes in temperature 

 of the Pacific were readily translated to the Tertiary floras of 

 western America, similar changes in the Atlantic from the 

 Eocene to Miocene epochs had less effect upon the Miocene 

 floras of central and eastern Asia because of its distance from the 

 region they occupied. In like manner many Miocene genera, par- 

 ticularly of deciduous types, have survived to the Recent in the 

 temperate parts of eastern Asia. The living forests of northern 

 Japan, Korea, Manchuria, and northern China, as observed by 

 the writer, have a definitely Miocene aspect. The resemblance of 

 these forests to those of eastern North America was long ago 

 recognized by Asa Gray,"'' who suggested a past interchange of 

 vegetation between the two areas across high latitudes. In the 

 light of modern studies of later Tertiary floras and their distribu- 

 tion, it seems possible to conclude that this deciduous element, 

 comprising genera and species from both sides of the Pacific, has 

 survived on the eastern sides of both continents under climatic 

 conditions involving summer rain and winter cold. The gradual 

 elimination of deciduous types from the forest of the Pacific 

 Coast, with the resultant dominance of broad-leafed evergreens, 

 has resulted from the development there of a climate character- 

 ized by mild, rainy winters and cool, dry summers. 



Comparison of the list of older Tertiary families and genera of 

 Oregon and California (pp. 58-59), and of the list of Miocene 

 families and genera (pp. 68-69), emphasizes that there is a great 

 difference in their composition. With unimportant exceptions, 

 the families and genera of the Eocene have their most extensive 

 modern development in the warmer parts of the world, while 



