92 NOTICES OF BOOKS 



* 



22, we find that the "nervi liberi" and the "nervi anastomosantes " 

 are the primary points upon which his division of the genus Polypod'wm 

 is made to rest. This is a kind of reasoning we do not understand, for 

 if these characters were so artificial as to be unfit for generic purposes, 

 why apply them for subgeneric? If they broke down in the one place, 

 surely they will break down in the other. 



Having shown the insufficiency of the characters derived from the 

 free and anastomosing veins, he considers the articulation of the petiole, 

 to which however he is not inclined, in the present state of our know- 

 ledge, to attach any generic importance. He does not seem to be 

 aware that the latter character is always accompanied by others,! as 

 has been pointed out by Newman and J. Smith. The division of the 

 frond, the articulation or non-articulation of the pinnules, and the 

 difformity of the fertile and sterile fronds, are also rejected as ge- 

 neric characters. The epidermidal organs, and the sporangium in 

 all its bearings, are then fully discussed, and a great many facts in- 

 validating various generic characters derived from them, are brought 

 forward. 



Of the enumeration of the species, the specimens preserved in 

 Kunze's Herbarium form the chief basis, and diagnoses are given of 

 them. Of the species described by Dr. Mettenius in other publications, 

 we have only the uames, and the same is the case with those known to 

 him merely from figures or descriptions. The latter are inserted in a 

 mariner which requires a little explanation. Thus, for instance, his 

 No. 100 is Polypodium incamm, Sw., with four varieties (a, /3, y, 8) ; 

 then follows "(100 5) P. microlepis, Fee;" "(100c) P. remotum, 

 Desv.;" and " (100 d) P. lanosum, Fee." Many would take these to 

 be anything but what the author means them to be, viz. allied species 

 (though assuredly, to our own knowledge, many of them very distinct) 

 of which he has merely seen a figure or description. It may also be 

 remarked that the "enumeration" does not include all the species pub- 

 lished during the last two or three years. Polypodium, as here given, 



* It will readily be seen that our friend who obligingly communicated this notice 

 is favourable to the great multiplication of genera of the present day ; but we do 

 not at all agree with him that because certain characters are not of sufficient impor- 

 tance to constitute genera, they are equally inefficient for sectional characters or 

 subgenera. The same kind of argument would equally apply to species, and conse- 

 quently even pecies would become a genus. — Ed. ' 



f Is it real I v so? — En. 



