— 20 — 



accuracy." At the same time both Fee and Presl put the plant 

 in Polypodium (Goniopleris), following Schwartz, who originally 

 named the species. Again under Phegopteris rigidum, in the 

 44 Synopsis Filicum," it is stated that the species is " very varia- 

 ble, the forms differing only by the want of an involucre from 

 the forms of Aspidium aculeatwn, to which it shouid probably 

 be joined." Also in Mr. Baker's "New Ferns," published as late 

 as 1892, he says of Nephr odium hastatum Jenmani : 14 1 believe 

 it is an indusiate form of Polypodium obliteratum Swartz.'' 

 And finally, at the beginning of Nephr odium in 44 Synopsis Fili- 

 cum," it is stated that 44 it is perhaps scarcely needful to warn the 

 young student to bear constantly in mind that an Aspidium with 

 an abortive or obliterated involucre is not distinguishable from a 

 Desmobryoid Polypodium." 



On June 22, 1898, 1 gathered a plant of Dryopteris Novebora- 

 censis, on which there were two sterile and two fertile fronds. 

 One of the latter is perfectly normal and possesses distinct sori, 

 with beautifully developed indusia. The other has the sori 

 grouped as thickly as they can lie, with not aji indusimn on them. 

 The time of year when gathered and the green appearance of the 

 sori testify to the youth of both fronds, so there can be no ques- 

 tion raised as to the indusium having disappeared. Thus, on the 

 same plant, there is an indusiate and a non-indusiate frond. Here 

 is an example right from nature to show how unreliable is the in- 

 dusium as a broad distinction between genera. A generic de- 

 scription should certainly be composed of the most stable and 

 uniform characters belonging to a certain group of plants, and 

 this is what cannot be predicated of the organ called an indusium. 



When we come to the distinction drawn by Hooker, both in 

 his 44 Species Filicum" and in the ''Synopsis," between Aspid- 

 ium and Nephr odium, viz., a peltate involucre for Aspidium and 

 a kidney-shaped one for Nephrodium, we find even Mr. Baker in 

 his 44 New Ferns," declaring, 44 I should not in a new book keep 

 up Aspidinm and Nephrodium as genera." The change which 

 has been made from these genera to Dryopteris, therefore, seems 

 to have the sanction of the best authority in England, at least in 

 a negative manner. 



All this goes to show that Phegopteris can only be told from 

 Nephrodium (Lastrcea), and Goniopteris from Eu- Nephrodium 

 by the presence or absence of an involucre ; and that in a num- 

 ber of cases where it is doubtful whether an involucre exists, the 



