84 m. INTEODUCED SPECIES. 



entertained, after long and careful investigation of the 

 subject, by a botanist so deservedly inheriting and sup- 

 porting a name of world-wide celebrity. Before giving 

 his views in regard to individual species, which is in- 

 tended to be done presently for the sake of comparison 

 with those intimated in the Cj^bele, it may be well to 

 make some comments on the method pursued by M. De 

 Candolle, and to inquire how far it is calculated to lead 

 him to satisfactory conclusions. 



The distinction between original natives and introduced 

 species, is one of primary importance in geographical bo- 

 tany. On this account the modes and indications resorted 

 to, for separating plants into the two classes, require to 

 be well considered and agreed upon. Botanists cannot 

 yet be said to have fixed rules ; although the course of 

 investigation followed by M. De Candolle in his inquiries, 

 does in some measure prescribe such rules or assumed 

 principles. The present writer and M. De Candolle are 

 clearly somewhat opposed in the comparative value or 

 importance which they attach to the rules so set forth by 

 the latter. They differ in regard to the data or evidences 

 on which a reliance should be chiefly placed, in attempt- 

 ing to decide whether given species are native or other- 

 wise in England and elsewhere. 



For example, M. De Candolle arrives at some of his 

 conclusions, by comparing together the opinions of dif- 

 ferent English botanists. When those opinions are alike, 

 they may then be held evidences entitled to attention. 

 But when those oi^inions conflict, how can a foreigner 

 then decide between them ? He must attempt to do so 

 under great disadvantages, in not being sufficiently aware 

 of the relative degree of trust which ought to be given to 

 the statements and inferences of different botanists here. 

 These disadvantages appear to affect unfavorably the 



