III. INTRODUCED SPECIES. 69 



by which the introcluced species can be again divided 

 into naturalised and non-naturalised. This is hopeless. 

 The first difficulty is little likely to be surmounted for 

 a long time to come, that of distinguishing between na- 

 tive and introduced species. The more completely a 

 foreign species becomes naturalised, the greater becomes 

 the inclination of English botanists to place it among the 

 true natives ; so that we find some of them now treating 

 the parsley and wall-flower as true natives. And thus 

 naturalisation is converted into nativity, so far as mere 

 opinion can effect such a conversion. 



In former volumes of this work citations were fre- 

 quently made about the indications of nativity or other- 

 wise, as given in the general Floras of Britain, and also 

 of those put forth by some local botanists. It was thus 

 shown that such indications are often in direct contradic- 

 tion to each other. When not in opposition, the seeming 

 harmony too often had been occasioned by writers copy- 

 ing from one book into another. Dr. Bromfield rightly 

 conjectured the chief reason for adducing those contrasts 

 of opinion. It was seldom done with any idea of attaching 

 much authoritative value to the discordant opinions so 

 brought together. More usually it was done expressly 

 for the purpose of showing that the chance opinions of 

 closet botanists are too contradictory to be of any real 

 value. Such are designated the chance opinions of 

 closet botanists, because too frequently they were put 

 forth by those who had neither seen the localities of the 

 plants, nor had properly examined the evidences on 

 which their decisions ought to have been given. 



The attempt of Professor Henslow, in his Catalogue of 

 British Plants, dated in 1835, was doubtless much im- 

 peded by the imperfect and often erroneous indications 

 given in the general Floras, as well as by the conceal- 



