Geographical Distribution of Indigenous Plants. 51 
: oN THE GHOGRAPHICAL “DISTRIBUTION OF THE 
_ INDIGENOUS PLANTS OF HUROPE AND THE 
NORTHEAST UNITED STATES. 
By JosepH F. James. 
‘It has long been a matter of considerable interest to botanists, to 
| observe the fact that in every country there are found some species of 
plants common to some other country, perhaps thousands of miles 
away ; and much speculation has been indulged in to account for the 
causes which have led to this apparently capricious distribution. The 
subject of the Geographical Distribution of Plants has occupied the 
minds of some of the most eminent men of our time, and Humboldt, 
De Candolle,“Hooker, and Gray, have followed one another in rapid 
succession. Much as has been done, still more remains, and I purpose 
as a contribution to the subject, to take a view of the Geographical | 
Distribution of the Indigenous Plants common to Europe and the 
Northeast United States,,and to indicate the reasons for the resem- 
- blances between the floras of the two continents. 
Modern science. has been so revolutionized in the last twenty. years, 
caused primarily by the publication of the “ Origin of Species,” that 
scarcely. any one now believes in the assertion of an eminent au- 
. thority,* that “there is indeed nothing more easy to perceive, in the 
distribution of organic beings over the globe, than the universal 
law, that nature, in similar circumstances, has always produced similar 
or perfectly the same creatures.” Such used to be the belief, but now 
there are but few scientific men who do not believe in the evolutionary 
_ hypothesis as postulated by Darwin ; who do not-believe, as Wallace 
has expressed it, that “every species has come into existence, coin- 
cident both in-space and time with a pre-existing closely allied 
species.”+ Therefore, when we find identical species in two different 
quarters of the globe, we believe the individuals in both localities to 
_ be descended from a common parent. 
In order to account for many facts in the distribution of plants and 
- animals, long periods of time must be allowed. There is no evidence 
to prove that the American continent is of such recent origin as to 
~ merit the title of “ New,” in contra- distinction to the “ Old World.”. On | 
the contrary, the evidence points in the other direction. Geologists 
gener ally have now come to the conclusion that the great land masses 
oe Meyen, Geog. of Plants, Pub: of Ray Society, 1846, p. 2657 
+ Wallace, Contr. to Nat. Selec., N. Y., 1871, P 5. 
