56 FERNS : BRITISH AND FOREIGN. 



ON THE GENERA OF FERNS AND THEIR 

 CLASSIFICATION. 



''■"'HE systems for the classification of Ferns are 

 -*- almost as numerou s as pteridologists themselves ; 

 indeed, nearly every author, from Linnasus downwards, 

 who has written upon the subject, has propounded his 

 own views, and these have generally differed both 

 from his predecessors and from his contemporaries. 

 But the point upon which pteridologists appear to differ 

 most, and on which their only agreement seems to be 

 an agreement to differ, is the definition of genera and 

 theii: limits. I say emphatically appear to differ, for 

 in the works of those most at issue, the differences are 

 not so much in the limits of the groups themselves 

 as in the relative importance assigned to them. For 

 example, while some, as Presl, Moore, and myself, 

 break up the old Linusean genera, Polypodium, Aspi- 

 diwm, &c., into a greater or lesser number of smaller 

 genera, others, as Hooker and Mettenius, prefer ad- 

 hering to the Linnsean genera, without greatly altering 

 their characters, and adopting the modern generic 

 names as sectional ones for such divisions as they find 

 themselves compelled to make. It would occupy too 

 much space to enter fully upon this subject, and I 

 must leave it for a more extensive work upon the 

 genera of Ferns, long contemplated by me, con- 

 tenting myself here with a brief mention of the organs 

 more or less employed by pteridologists in establish- 

 ing and classifying genera. 



