NOTICES OF BOOKS. 91 



In conclusion, with every respect for Dr. Hoffmann's industry and 

 perseverance, we cannot avoid coming to the conclusion that we should 

 have preferred finding the results of his labours in a communication to 

 the 'Monatsbericht' of the Berlin Academy, for neither their interest 

 nor importance demanded their publication in extenso. 



Ueber einige Fakngattungen {On some Genera of Ferns). I. Poly- 

 podium. By G. Mettenius. (Extracted from the second volume 

 of the Transactions of the Senkenbergian Society of Natural His- 

 tory). Frank for t-on-the-Main, 1856. 



Dr. Mettenius thinks that in order to test the soundness of the views 

 which have led modern pteridologists either to subdivide or to pre- 

 serve the limits of the old genera of Ferns, Polypodium offers the best 

 and most ready means; and he consequently commences his Paper 

 with an enumeration of the species of that genus, prefaced by a critical 

 review of the various organs upon which the generic distinctions of 

 •Polypodies have been founded. He does not give in this place, we 

 regret to say, the characters which he considers typical of his Polypo- 

 dium, but refers us for them to his work entitled 'Die Fame des Bo- 

 tanischen Gartens zu Leipzig ' (' The Ferns of the Botanic Garden at 

 Leipzig'), published in 1856, so that we have to study his views con- 

 tained in the first seventeen quarto pages of the present work, before 

 we gain any knowledge on that point. The drift of his argument 

 seems to be this, viz. that the importance of various organs as generic 

 characters has been very much overrated, and that in consequence, 

 too many genera have been made. These he labours to abolish by 

 pointing out numerous transitions from one state or form of an organ 

 to another. However it must be confessed that in many places he 

 argues against himself, by adopting in the synoptical part of his Paper, 

 the very characters for subdivisions which he shows to be invalid for 

 the circumscription of genera. Thus, for instance, when speaking of 

 the value of the free and anastomosing veins, he says, "The facts 

 quoted sufficiently prove the correctness of my views, that neither be- 

 tween the species with a different development of the free veins, nor 

 between the species with free and anastomosing veins, can there be 

 drawn any natural boundaries " (p. 3). Yrt, on turning to pp. 1 7 and 



