410 
APPENDIX D. 
(D, p. 141). 
On Woodsia, a 7iew Genus of Ferns. By Robert Brown, Esq.,F.R.S., 
Lib. L.S. (From tbe Linnean Transactions, xi. 170). 
There is perhaps no tribe of Cryptogamous plants which, since the time of 
Linneus, has received greater additions to its number of species, or more consi- 
derable improvements in its systematic arrangement than the Filices : and cer- 
tainly no botanist has so essentially contributed to those improvements as the 
President of this Society ; whose ingenious ‘ Essay on Dorsiferous Ferns’ may 
be justly considered as the groundwork of the more complete dissertations of 
Professors Swartz and Bernhardi, which have appeared since its publication.^ 
Linneus, in his latest work, the 13th edition of the ‘ Systema Vegetabilium,’ 
enumerates scarcely more than two hundred ferns, which he referred to twelve 
genera ; while the ‘ Species Plantarum ’ of the late Professor Willdenow con- 
tains upwards of a thousand plants of the same order, arranged under forty- 
three genera. It is, however, remarkable, that of this vast number of species 
nearly one half belong to four of the Linnean genera, namely. Polypodium, 
Acrostichum, Asplenium and Pteris, all of which were first proposed by Ray in 
his ‘ Methodus Plantarum Emendata,’ published in 1703 ; without names in- 
deed, 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 per- 
fection as to supersede all changes in nomenclature, may be inferred from the 
genus Polypodium alone, though reduced nearly one-half by its present charac- 
ter, still including a hundred and fifty seven species, or upwards of a seventh 
part of the whole order. 
The expediency of subdividing Polypodium, as well as some of the other 
genera mentioned, especially Acrostichum, is indeed obvious, not merely on ac- 
count of their great extent, but also from the striking differences in habit exist- 
ing among the species referred to each. 
I have some time agof had an opportunity of remarking that two plants re- 
ferred to Polypodium — P. ilvense and hyperhoreum, form a distinct genus from 
the peculiar structure of their involucrum, even the existence of which had es- 
caped preceding observers. 
This genus I have named in honour of my friend Mr. Joseph Woods, whose 
merits as an accurate and skilful English botanist, are well known to many of 
the members of this Society: and the object of the present communication is to 
* An. 1794, in Mem. de I’Academie Royale des Sciences de Turin, v. 401. 
+ Prodr. El. Nov. Holl. i. 158 Obs. iv. 
