III. INTRODUCED srECIES. 125 



back to the earliest records of its occurrence in Britain ; 

 and also, when i^ossible, to its still earlier relics in peat- 

 mosses and elsewhere. The vast changes gradually 

 ■wrought in the vegetation of Britain, by the conversion of 

 forests into wastes, and of wastes into cultivated lands, 

 would also find appropriate place in a work of the kind 

 suggested. Such a history might be made a very valu- 

 able contribution to botanical science, — and likely enough 

 to geological science also. But it would require to be 

 written by a scrupulous investigator of facts, and a con- 

 scientious recorder of them. It would require to be wi-itten 

 under a higher impulse than that which prompts to the 

 compiling of ' Keys ' and ' Manuals ' for the market, — or 

 under a worthier ambition than that of " getting up some 

 sort of paper, likely to make a talk among the geologists, 

 at the next Meeting of the British Association." 



