INTRODUCTION. XVll 



Dr. J. D. Hooker. I have also introduced those 

 names of British ferns which are in general use with 

 fern cultivators, being guided chiefly by Mr. Moore's 

 * Nature-printed Ferns,' but have not gone into the 

 many synonyms. 



Our botanists of to-day find it necessary to reject 

 from the British Flora several plants that were 

 formerly admitted by mistake. Some have only 

 been recorded once several years ago, and the record 

 has not been verified by a specimen : such instances 

 may be fairly judged to be mere blunders. Other 

 plants that have been called British are escapes 

 from cultivation, and some are casual weeds that 

 have sprung from seeds or plants accidentally 

 imported with other foreign produce. Of these, a 

 few have established themselves to such an extent 

 that they may be considered permanent residents or 

 colonists ; as for instance the American plants Clay- 

 tonia perfoliata and Anacharis Alsinastrum. The 

 'London Catalogue of British Plants,' 6th ed., 

 excludes 269 species that have been formerly 

 admitted, viz. — of '' Aliens, Casuals, Waifs of Culti- 

 vation," &c., 115 ; and '*' Ambiguities, Errors, 

 Impositions, Extinctions," 154. I have not pur- 

 posely omitted the names of any well-known plants, 

 such as Datura Stramonium (Thorn-aj)ple), Poly- 

 gonum Fagopyrum (Buck-wiieat), Narcissus poeti- 

 cus, &c., though they are not indigenous British 

 plants. 



The present generic names are explained at 



