XV 111 



In like manner we know but of two Mayanthemum, five 

 Valtisnerias, and three Chestnuts ; and yet none of these 

 genera are confined to a single continent, but each is repre- 

 sented in the New World as well as in the Old. 



Indeed not only do the recognized effects of climate offer 

 no explanation of such facts, but we are driven to discard 

 all idea of accounting for them in this manner, when we find 

 that many plants, when transferred to a foreign soil, vegetate 

 even more luxuriantly than they do in their native country ; 

 thus proving the fallacy of any hypothesis which, assuming 

 their universal distribution in the first instance, should 

 attempt to ascribe their present limitation to the climate in 

 other localities being unfavourable to them. When we ob- 

 serve the pampas of Buenos Ayres covered over with Thistles 

 and Artichokes brought over by European settlers; when 

 we see the AnacJians Alsmastrum invading the ditches and 

 still rivers of Great Britain ; when we find the Canadian 

 Erigeron, which was conveyed to the Botanic Garden at 

 Paris little more than a century ago, now distributed over 

 the whole of Europe ; and the Plantain occurring so com- 

 monly, it is said, in America, wherever an Englishman has 

 trodden, as to have acquired amongst the Indians the name 

 of the Englishman's Poot, it is difficult to imagine that 



