152 NATURAL HISTORY BULLETIN. 



systematist than the Family Aspidiecz, and the writer does 

 not presume to be able to remove them. 



Unless the indusium is practically disregarded as a 

 generic character, as has been suggested by Gilbert* and 

 the group is subdivided on new lines, generic limitations 

 will remain more or less indefinite and unsatisfactory. But 

 so long as this character is employed there can be no 

 warrant for the union of Aspidium (restricted) and 

 Nephrodium under one generic name {Dryopteris Adan- 

 son, accordingtoKuntzef,) while Phegopteris is recognized 

 as a valid genus, for whatever may be the difficulty in 

 distinguishing between Aspidium (restricted) and Ne- 

 phrodium, it is even greater between Nephrodium and 

 Phegopteris. Yet much of this difficulty is due to 

 imperfect material, and a change in classification ought 

 scarcely to be demanded merely for the purpose of facilita- 

 ting the disposition of imperfect material. On the same 

 ground objection may be made to Diels' union of a part 

 of Phegopteris with Nep1irodium% while Po/ystiehum, 

 Aspidium, Nephrodium, etc. are recognized as genera. 



Whatever may be the difference of opinion as to the 

 name, the conviction that the group known as Polystichum 

 should constitute a distinct genus seems to be growing. 

 The habit of growth, texture, venation and distinctly 

 peltate indusium separate all of the species distinctly from 

 other members of the family, and Roth's name Polystichum 

 is probably the correct one for the genus. 



The generic name Dryopteris has been used in such a 

 variety of senses in recent years § that it is impossible to 

 determine its correct application from recent references, 



*Report of Boston Meeting-, Linnaean Fern Chapter, pp. 19-25 (1899). 



fBritton and Brown, 111. Flora, vol. i, (1896). Prof. Underwood has 

 since restricted Dryopteris to the species formerly included 

 under Nephrodium,-vide "Our Native Ferns," 6th ed., 1900. 



i.Nat. Pflanzenfamilien, 188-189 Lief., pp. 166, etseq. 



§See Britton and Brown, 1. c, Engler, 1. c, Underwood, 1. c, etc. 



