302 Wilson's filmy feen. 



With respect to the name, British authors seem agreed in 

 calling it H. Wilsoni ; but, numerous as are our descriptions 

 under this name, and excellent as is that by Mr. Wilson in the 

 ' Supplement to English Botany ' (E. B. S. 2686), stiU, not 

 one appears to me so exact and accurate as WiUdenow's, of his 

 species H. unilaterale, (Sp. PL v. 521). I have never seen 

 authentic specimens of WiUdenow's plant, which that author 

 does not mention as an inhabitant of Europe. 



The species, as British, was first distinguished from the pre- 

 ceding by Mr. Wilson, who, in a letter to me, observes : — "I 

 have had considerable difficulty from the very first in procur- 

 ing for Hymenophyllum Wilsoni [unilaterale] an exact descrip- 

 tion : the pinnae are not pinnatifid, as in H. tunbridgense, but 

 more properly of a lobed or triangular form (rhomboid Ln the 

 other species). It may perhaps aid the Olustration to say that 

 H. tunbridgense has the pinna with a central axis, while no- 

 thing of the sort can be detected in H. Wilsoni [unilaterale] ; 

 and that if you were to cut away the outer half of the pinna of 

 H. tunbridgense, you would then reduce it to the shape of H. 

 Wilsoni [unilaterale]. By this character the species may be 

 recognised in a barren state." 



The range of H. unilaterale is coextensive with that of H. 

 tunbridgense, it having been found in the most distant parts of 

 the globe ; and it is a circumstance worthy of note that the two 

 species are generally found growing near each other. H. uni- 

 laterale occurs in Europe, Africa, New Holland, and South 

 America. I have no Asiatic habitat ; and it is a little remark- 

 able that no Hymenophyllaceous plant is mentioned in the 

 ' Flora Eossica,' a carefully compiled Flora of a larger tract of 

 country than is contained in any other professing to be geogra- 

 phically or politically restricted. 



The range of this species in Great Britain appears to be 

 much more extensive than that of H. tunbridgense : it also 

 seems to be a more northern species, and generally to prefer 

 a greater elevation and more exposed sites : still, as already 



