III. FLORA OF BRITAIN. 393 



the progress of geographico -botanical science. The Au- 

 thor of this present work formerly entertained the hope 

 of being able to cai-ry out his conceptions in that form, 

 after concluding the Cybele Britannica ; this present 

 work being unavoidably limited to more partial views and 

 local details, than would have constituted the staple of 

 the more comprehensive treatise, long contemplated, and 

 reluctantly abandoned. The required time and requisite 

 mental vigour can no longer be reckoned upon. Such a 

 work ought to be undertaken by a younger botanist, who 

 might hope to devote thereto a dozen or a score of years 

 of active Hfe and earnest effort. If any botanist should 

 ever devote his time to such an undertaking, it will be 

 well for him to keep steadily in recollection, that a 

 volume of vague generalities would jDrove only worthless 

 to science ; while, on the other hand, crude details about 

 species, unsifted from errors, and not condensed into 

 tabulai" results, would be scarcely better. 



3. Number of Species. — The Flora of Britain must still 

 be deemed one of much uncertainty in respect to the 

 number of species which compose it. In too many in- 

 stances, as ah-eady much commented upon, botanists do 

 not agree on the questions, which ought to be accounted 

 the really natural species, and which among them are the 

 really native species ? These distinctions lie at the veiy 

 foundation of phyto-geographical investigations ; and it 

 is consequently most needful to know and appreciate the 

 grave difficulties which imperfect knowledge and contra- 

 dictory opinions still place in the way of such investiga- 

 tions. Those difficulties might gradually become much 

 lessened, if local and descriptive Floras were more usually 

 written by men of philosophic thought, competent to 

 reflect on what they observe, and to describe accordingly. 



VOL. IV. 3 E 



