134 
BRITISH FERNS. 
There is a variety of this fern which has the basal 
leaflets very deeply lobed, which Mr. Moore calls sub - 
tripinnatum . It is a very elegant form of the fern, being 
more lax than the normal form, and therefore more 
graceful ; besides which, the deeper divisions of the larger 
leaflets, which procure for it the name of “ rather tri- 
pinnate/ ; make it more feathery in appearance. 
NEPHRODIUM, Desv. 
(LiSTBEA.) 
Gen. Char . Sori roundish. Involucre kidney- or heart- 
shaped, attached to the frond at the indentation. 
This group was formerly called Aspidium , afterwards 
Lastrea , and now Nephrodium , Hooker. Its distinguish- 
ing characteristic is a notch in the otherwise round in- 
volucre, which changes the simple circle into a heart- 
or kidneyrshape. Many of the largest and most elegant 
ferns belong to this group. Nephrodium is from a Greek 
word signifying kidney , in allusion to the form of the 
involucre. 
13. Nephrodium Thelypteris. Marsh Buckler-fern. 
Caudex long, slender, branched, creeping. Stem distant, long. 
Fronds oblong-lanceolate, 1 to 2 feet long, pinnate. Pinnae 
horizontal, tapering. Veins forked. Sori in two rows on the 
leaflets. Involucres small, slightly toothed on the margin. 
The literal meaning of Thelypteris is Woman-fern , and 
probably refers to the slender growth of the plant. 
The caudex of this fern is black and slender, and it 
creeps as widely in its favourite marshy ground as the 
Oak-fern does in its shady woods ; it throws out nume- 
