70 III. INTRODUCED SPECIES. 



ments and omissions by the reporters of localities. And 

 making fair allowance for the then existing state of opi- 

 nion on the subject, and for the accumulated errors then 

 in print, it is worthy of note that the Professor should 

 have steered his course so well in 1835. What his ideas 

 were at that date will presently be shown in comparison 

 with those of the Cybele Britannica and Manual of 

 British Botany full twenty years later. Indeed, the Au- 

 thor of the Manual, edition of 1856, may in the main be 

 pronounced still considerably below the point already 

 reached by Professor Henslow in 1835. And yet the 

 Manual is certainly an impi'ovement, even in this respect, 

 on its predecessors among the descriptive Floras ; al- 

 though there is still ample room for further improvement. 

 Previously to the publication of the Manual of British 

 Botany the indications of nativity or non-nativity, in so 

 far as the general Floras were concerned, were little 

 better than idle guesses, usually hazarded without any 

 sufficient qualifications for judgment in their authors. 



Various are the grounds upon vs'hich the nativity of 

 plants in Britain may be doubted or denied. Very little 

 can usually be known about the pedigrees of plants which 

 are now observed to exist here more or less sponta- 

 neously. The doubts and denials are for the most part 

 retrospective inferences, deduced either from old records 

 or from present facts. And as the records and facts vary 

 greatly in their completeness and certainty, the most sin- 

 cere and cautious seekers for truth may reasonably be 

 expected to differ in the conclusions deduced from them. 

 Thus much appears quite true as a general rule, that bo- 

 tanists of small experience are the most prone to pro- 

 nounce plants " truly indigenous." If some few among 

 the more advanced botanists have continued to evince a 

 disj)Osition to the like hasty conclusions, this peculiarity 



