44 



PHYTOGEOGRAPIIY AND EXPLORATION 



Asa Gray 



The Similarity Between the Flora of Japan and 

 that of the United States, Epecially the Atlantic Side 



Reprinted with the permission of the pub- 

 lisher from Darwinians. New York, D. Ap- 

 pleton Co., 1889. 



If we now compare, as to their flora 

 generally, the atlantic United States 

 with Japan, Manchuria, and north- 

 ern China— i.e., eastern North Amer- 

 ica with eastern North Asia, half the 

 earth's circumference apart— we find 

 an astonishing similarity. The larger 

 part of the genera of our own region, 

 which I have enumerated as wanting 

 in California, are present in Japan or 

 Manchuria, along with many other 

 peculiar plants, divided between the 

 two. There are plants enough of the 

 one region which have no representa- 

 tives in the other, lliere are t\pes 

 which appear to have reached the At- 

 lantic States from the south; and there 

 is a larger infusion of subtropical Asi- 

 atic t}'pes into temperate China and 

 Japan; among these there is no relation- 

 ship between the two countries to speak 

 of. There arc also, as I have already 

 said, no small number of genera and 

 some species which, being common all 



round or partly round the northern 

 temperate zone, have no special signifi- 

 cance because of their occurence in 

 these two antipodal floras, although 

 they have testimony to bear upon the 

 general question of geographical dis- 

 tribution. The point to be remarked is, 

 that many, or even most, of the genera 

 and species which are peculiar to North 

 America as compared with the Califor- 

 nian region, are also represented in 

 Japan and Manchuria, cither by iden- 

 tical or by closely similar forms! Tlie 

 same rule holds on a more northward 

 line, although not so strikingly. If we 

 compare the plants, say of New Eng- 

 land and Pennsylvania (latitude 45°- 

 47°), with those of Oregon, and then 

 with those of northeastern Asia, we 

 shall find manv of our own curiously re- 

 peated in the latter, while onh^ a small 

 number of them can be traced along 

 the route even so far as the western 

 slope of the Rocky Mountains. And 



