ON WOODSIA. 253 



The difficulty, too, of separating the membrane entire 

 from the frond, to which, by the pressure of the capsules, 

 it is closely applied, is so considerable, that, since the pub- 

 lication of my remark already quoted, its existence has 

 been doubted by a botanist, whose opinion, especially in 

 whatever regards this order of plants, is of peculiar weight, 

 and in opposition to which I should not retain full con- 

 fidence in my own observations, though frequently repeated, 

 were they not so distinctly confirmed by Mr. Bauer's ex- 

 cellent drawing. 



I first observed the involucrum six years ago in living 

 plants of Woodsia hyperborea, and have since repeatedly 

 ascertained its existence in dried specimens of the same 

 species, and of Woodsia ilvensis. These two plants are 

 indeed so nearly related, that I find myself unable to con- 

 struct for them clear specific characters ; and therefore, in 

 proposing them here as distinct species, I am, from want 

 of sufficient materials to determine the question, rather fol- 

 lowing the prevailing opinion than my own. 



To the characters and synonyms which follow, I have 

 not thought it necessary to add descriptions of the two 

 supposed species, these having been given by several of 

 the authors referred to, and in every respect correctly, 

 except what regards the involucrum. 



Woodsia. cits 



Sori dorsales, subrotundi. 



Involucrum calyciforme apertum margine crinitum : in- 

 cludens Cccpsulas pedicellatas : receptaculo communi elevato 

 nullo. 



Eiliculse, frondibus ccespitosis, pinnatim divisis ; pills 

 simplicibus squamidisque angustis instructs. 



1. ilvensis. W. frondibus bipinnatifidis, pinnis oblongis, 

 pinnulis confluentibus multifloris : inferioribus subrepandis : 

 infimis subaequalibus. 



Polypodium ilvense, Swarlz, Synop. Fil. 39. Willden. 

 Sp. PL 5, p. 198. Schkuhr, Crypt. 16, I 19. 



