278 THE BRITISH FERNS. 
than as distinctions of generic importance. In one group, $ Woodsia, 
which may be considered typical of the genus, and which is repre- 
sented by our two native species, the involucres are very small 
and pateriform (dish-like) with a prominent fringed margin of 
incurved hair-like segments. In another group, 8 Perrinia, repre- 
sented by the North American W. obtusa, the involucres are larger 
sub-hemispherical and broken at the edges into four or five irregular 
lobes. In the$ Physematium, represented by W. mollis of Mexico, 
the involucres are subglobose, with a contracted mouth at the apex. 
There is considerable difference of appearance between the two 
extremes of form here indicated, but they seem sufficiently recon- 
ciled by the intermediate group, and Woodsia proper may be re- 
garded as having the sub-globose involucre of Physematium split at the 
margin into criniform incurved segments, thus retaining in some 
measure the cup-shaped character. 
The genus Woodsia is the British representative of the sectional 
group Peranemeœ, which includes in addition two or three small 
exotic families. 
The generic name is given in compliment to Mr. Joseph Woods, 
a veteran British botanist. 
BRITISH SPECIES. 
W. ilvensis: fronds oblong-lanceolate, subulately squamose; pinne oblong or 
ovate-oblong obtuse ; stipes and rachis crinite chaffy. 
W. alpina: fronds linear, slightly hairy not scaly; pinne triangular ovate 
obtuse ; stipes and rachis slightly hairy. 

