24 . 
THE OBLONG WOODSIA. 
Woodsia ilvensis. 
Plate 0 , Fig. 5 , Page 235 . 
The only British representatives of the genus Woodsia art* 
two diminutive, beautiful and extremely rare little Ferns. 
This generic designation is not descriptive but commemora- 
tive, having been suggested in compliment to Joseph Woods, 
an English botanist. The peculiar nature and construction 
of the indusium in these Ferns give to them a very distinct 
character and separate them from anything like close con- 
nexion with any of the other British species. We have seen 
that in the ease of most Ferns the indusium is merely a cover 
to the sorus, or heap of spore cases, whether this cover be 
formed by a special organ like the flat scale in the Shield 
Ferns and the inflated hood-like scale in the Bladder Ferns, 
or by a bending back of the margin of the frond. In the 
Woodsias the indusium is in the form of a concave scale, 
which lying under the clusters of spore cases is provided with 
a. fringed margin, which spreads over them. The specific 
name ilvensis applied to the present species, refers to the 
island of Elba where this Fern was first discovered. Woodsia 
ilvensis is an inhabitant of mountainous districts, where it is 
found growing in the moist crevices of rocks at altitudes 
ran pi no; from twelve hundred to two thousand feet above the 
sea level. 
Description. — A small-tufted rootstock provided with 
