NEPHRODIUM. 



463 



and that no doubt more will be added to the list. In one form or another 

 this genus is represented in nearly every part of the world. 



A comprehensive classification of such an extensive group of plants 

 required its division into various sections : accordingly there have been 

 numerous sub-divisions of the genus such as the following, which for want 

 of really permanent and distinguishable characters have now been abandoned. 

 The principal of these were : Ahacopteris, Fee ; Amaurojjelta, Kunze ; 

 Anisocampium, Presl ; Arthropteris, J. Smith ; Camptodium, Fee ; I)idosodo?i, 

 Moore ; Dryopteris, Schott ; Haplodictyum, Presl ; ffemestheum, Newman ; 

 Hypodematium, Kunze ; Lop)hodium^ Newman ; Pachyderis, J. Smith ; 

 Phegopteris, Fee ; Podopeltis, Fee ; Proferea^ Presl ; Pycnopteris, Moore. 



As the genus Nephrodium at present stands, it is divided, according to 

 the various kinds of venation observable in its species, into four distinct 

 groups as follow : 



EuNEPHRODiuM (Eu-neph-ro'-di-um), or true Neplirodium^ Richard. The 

 plants forming this group have only their lower veinlets united. 



Lastrea (Las'-tre-a), Presl. In this group the plants have all their 

 veinlets free. 



Pleocnemia (Ple-oc-ne'-mi-a), Presl. In these plants the lower veinlets 

 of contiguous groups are united, and, being pinnate in the lobes, form 

 central arches. 



Sagenia (Sag-e'-ni-a), Presl. All the veins in the plants of which this 

 distinct group is composed are anastomosing (copiously intercrossing each 

 other) ; they usually have free included veinlets. 



The group Lastrea — by far the most important — is, for purposes ot 

 classification, subdivided into sections as follow : 



I. Plants with fronds not cut down to the main rachis (stalk of their 

 leafy portion), such as N. decursivo-pinnatum (popularly known under the 

 name of Lastrea decurrens). 



II. Species whose fronds have their leaflets either entire (undivided) or 

 lobed less than one-third of the way down to the midrib, as observed in 

 N. (^Lastrea) cuspidatum. 



III. The plants belonging to this section have their leaflets cut more than 

 half-way down to the midrib into close, regular, entire or nearly entire lobes. 

 The involucre in many, but not all the species, is thin and fugacious (not 



