THE ANCIENT AND INIODERN FLORAS OF MONTPELLIER. 213 



planted ; three, of which two are American, spread slowly over 

 suitable stations, but may probably never become very general ; and 

 seven, all American, have established themselves over large spaces 

 as weeds of cultivation very difficult to extirpate, so as to form a 

 prominent feature in the vegetation of the country. 



Finally, this preponderance of American species in the new intro- 

 ductions is explained by the consideration that those from other 

 countries (chiefly the Mediterranean region) having availed them- 

 selves of frequent opportunities of introduction ofiered to them for 

 ages previous to the period under consideration, cannot, if now 

 again brought in, be distinguished from the natural vegetation, of 

 which they have become a part, whilst the introduction of American 

 ones can only have commenced with the sixteenth century. 



It might not be uninteresting to devote a short space to the 

 consideration of how far the above general conclusions may be com- 

 pared to what is taking place in our own country — to what extent 

 the same general laws prevail in a region so very diff'erent from that 

 of Mediterranean France, as well as to climate and other physical 

 conditions, as in the degree to which it is affected by human agency. 

 "We all hear of the " vast changes" alluded to by Hewett Watson, 

 as " gradually wrought in the vegetation of Britain by the conversion 

 of forests into wastes, and of wastes into cultivated lands." We 

 know that within Dr. Planchon's period of three centuries, on the 

 one hand, the efforts directly or indirectly applied to the extirpation 

 as well of native as of involuntarily introduced species ; and on the 

 other, the opportunities afforded by an extended commerce, and a 

 varied and general cultivation of exotics, for the introduction of new 

 ones, have been infinitely greater in Britain than what has taken place 

 at Montpellier. There may be some difficulty in collecting all the data 

 recorded in various works which might guide us in the inquiry ; and 

 we have as yet no history of the British Flora which should, in the 

 words of Hewett Watson, " trace out each species back to the 

 earliest records of its occurrence in Britain, and also, when possible, 

 to its still earlier relics in peat mosses and elsewhere." Yet a few 

 facts which may be considered as well authenticated, may be suffi- 

 cient to show that the operations of nature in this respect are as 

 slow in Britain as at Montpellier, and that, independently always of 

 the plants actually and intentionally under cultivation, the spon- 

 taneous vegetation of our country has been much less affected by 

 the vicissitudes of three centuries than many may have imagined. 



