VEGETATION OF THE NORTHERN SHORES. 187 



belong originally to both hemispheres,* but were introduced into 

 America since the settlement of Europeans in this part of the world, 

 many of which, though foreigners, have spread so extensively, as 

 to be generally considered as natives of this country. But if we 

 carefully examine their distribution, we soon perceive that they follow 

 everywhere the tracks of civilization, and occur nowhere except in 

 those districts and in those soils where the hands of white men have 

 been at work. In such localities, however, they have almost com- 

 pletely replaced the native weeds, which have disappeared before 

 them as completely as the Indian tribes have disappeared before the 

 pressing invasion of the more civilized nations. These plants are 

 chiefly such as occur in Europe by the road-sides, or near the habita- 

 tion of man, and which to a certain degree may be considered as sat- 

 ellites of the white race. Their occurrence is particularly striking 

 along the new lines of railroads, where they settle almost as soon as 

 the tracks are marked out, and increase in a few years so rapidly 

 within the enclosure of the roads, as to suppress the primitive vegeta- 

 tion almost completely, with the exception of a few hardy natives 

 which resist the new invaders. Several of these plants occur natur- 

 ally, in America, in more northern latitudes. Nevertheless, I have 

 no doubt that in most cases they were introduced into the more 

 temperate and cultivated latitudes from Europe, rather than from 

 their northern residence in America. 



The following list of these plants was chiefly made from an 

 examination of the railroad tracks between Boston and Salem, in 

 company with that liberal cultivator of botany, Hon. John A. Lowell, 

 and also from materials collected during an excursion made with 



* I do not wish by this remark to be understood as intending to deny the identity of any 

 native plant in the temperate zone of Europe and America. I know^that many species 

 which occur very far north, and are there truly identical in both continents, are also 

 found among the plants of the temperate zone on the two sides of the Atlantic ; but 

 there still remains a large number, the identity of which ought to be ascertained by 

 direct comparison of authentic specimens from the two continents, before it can be 

 finally admitted that there" is no specific difference between them. As such, I may 

 mention Hepatica triloba, Geranium Robertianum, Oxalis Acetosella, Spiraea Aruncus, 

 Circoca lutetiana, Calystegia sepium, Agrimonia Eupatoria, Majanthemum bifolium, 

 and many aquatic plants. The identity of these with European species seems to 

 me the more questionable, as the freshwater animals, the fishes, mollusks and insects 

 differ specifically throughout. 



