IMPROVEMENT IN THE ARRANGEMENT OF FERNS. 369 



publication of Koth's Flora.* At all events, Swartz's name has thus 

 far almost universally prevailed ; and the genus, as defined by him, 

 needing sub-division, Polystichum has been adopted for a well marked 

 portion of it, an arrangement v?hich it would be very inconvenient now 

 to disturb. Sir W. J. Hooker, refusing to accept venation as a generic 

 character, limits Aspidium to species with a centrally attached indusium, 

 and adopts Nephrodium for those with a kidney-shaped indusium 

 attached at a point in the margin ; but be gives Polystichum as a sub- 

 genus or section of Aspidium, in the sense already explained as includ- 

 ing free fork-veined species with a centrally attached indusium, and he 

 employs Lastrea in like manner as a sub-genus of Nephrodium. I have 

 already said that I cannot admit the objection to the use of venation as 

 a generic character in ferns, and I think the distinguished author of the 

 ''Species Filicum" would have done better had he raised his &ub-genera 

 to the rank of genera. His method, however, practically marks the 

 distinction and employs the names. I cannot think that any number of 

 botanists will sanction the restoration of Polystichum in its original 

 sense, as taking the place in a great degree of Swartz's Aspidium, since 

 the other genera, as proposed by Roth at the same time, to complete 

 his view of this group of ferns, hardly can be received; and if we 

 admitted Polystichum as entitled to supersede Aspidium, our first 

 business, in the present state of our knowledge, would be to sub-divide 

 it into better limited genera, at the risk of causing inextricable confu- 

 sion. In its more limited sense, Polystichum is needed, and our Flora 

 affords fine examples of it. I would strongly recommend the adoption 

 of the name Lastrea for the free-veined Aspidiinas with a kidney-shaped 

 indusium attached by a lateral point, and Polystichum for free-veined 

 Aspidiinae with a peltate or centrally attached indusium, believing this 

 plan to be justified on scientific principles, and practically the most 

 intelligible and convenient. 



* I am aware of no ground whatever for the assertion made, I think too hastily, in the paper 

 referred to in the Canadian Naturalist, that " Swartz copied Roth throughout, borrowed his 

 genus, calling it Aspidium," &c. Swartz's Aspidium is not coextensive with Both's Poly- 

 stichum, and so far as I can trace the evidence, his paper was written without knowledge of 

 Eoth's work. 



