CHAPTER XLIL 



NEPHRODIUM, Richard. 

 (Neph-ro'-di-um. ) 

 BucUer Ferns. 



HIS genus, which derives its name from nephros, a kidney, in 

 reference to the shape of its spore cases, is a very important 

 portion of the tribe AsjJidiece, which, on account of the 

 character furnished by the shape of the involucre (covering 

 of the spore masses) of the various plants which it comprises, 

 has been divided, besides three small groups, into two large genera, viz. : 

 Aspidium proper, in which the involucre, round and terminal on the veinlets, 

 is fixed by the centre, and Nephrodium, an extensive group of plants, which 

 in Hooker and Baker's " Synopsis Filicum " forms Genus 44, and which 

 comprises about 300 species, varying much in size, texture, cutting, and 

 venation. The plants belonging to the tribe Asjjidiece are distinguished 

 principally by their sub-globose sori (nearly round spore masses), terminal on 

 the veinlets, and furnished with a cordate-reniform (between heart- and kidney- 

 shaped) involucre, which is attached to the frond by the sinus (depression). 

 The two genera thus formed have a closely similar range of variation in 

 cutting and venation, and it is by no means clear in which of the two several 

 species should be placed. It must also be borne in mind that an Aspidium 

 with an abortive or obliterated involucre is not distinguishable from a 

 Polypodium, that the number of species which have been originally 

 described as non-indusiate, in which a more or less (often very slightly) 

 developed involucre has been afterwards found to exist, is very considerable. 



