Mr. Brown on Woodsia, a new Genus of Ferns. 171 
without names, indeed, but with characters nearly similar to 
those of Linneus. 
It appears, therefore, that the arrangement of Ferns at present 
universally followed is not wholly new: and that it has not 
attained such a degree of perfection as to supersede all changes 
in nomenclature, may be inferred from the genus Polypodium 
alone, though reduced nearly one-half. by its present character, 
still including 157 species, or upwards of a seventh part of the 
whole order. 
The expediency of subdividing Béiysodism as well as some 
of the other genera mentioned, especially Acrostichum, is indeed 
obvious, not merely on account of their great extent, but also 
from the striking differences in habit existing among the species 
referred to each. 
I have, some time ago*, had an opportunity of remarking, that 
two plants referred to Polypodium, P.ilvense and hyperboreum, form 
a distinct genus, from the peculiar structure of their involucrum, 
even the existence of which had escaped preceding observers. 
This genus I have named in honour of my friend Mr. Joseph 
Woods, whose merits as an accurate and skilful English bo- 
tanist are well known to many of the members of this Society : 
and the object of the present communication is to illustrate it by 
some additional observations on its structure, and by a very per- 
fect drawing, for which I am indebted to the friendship of 
Mr. Francis Bauer. 
The character distinguishing Woodsia from all other genera 
of Ferns hitherto established, consists in its involucrum being 
inserted under the group of capsules, or, as it is technically 
called, the sorus, which it completely surrounds at the base; 
while it is in every stage open at top, having its margin divided 
* Prodr. Fl, Nov, Holl. 1. p. 158, Obs. iv. ; 
z2 = into 
