52 HISTORY OF BRITISH FERNS. 
14. Woodsia = Dorsal-fruited Ferns, having the indusia 
involucriform, Le. attached beneath the sori, and 
divided at the margin into hair-like incurved seg- 
ments. 
§ HYMENOPHYLLE^ = Ferns whose sori are pro- 
duced around the ends of reins projecting from the 
margin^ and surrounded hy urn-shaped or two-rahed 
membranes. It contains the genera Trichomanes and 
Hymenophyllum. 
15. Trichomanes = Marginal-fruited Ferns, having the 
sori surrounded by urn-shaped expansions of the 
frond. 
16. Hymenophyllum = Marginal-fruited Ferns, having 
the sori surrounded «by two-valved expansions of the 
frond. 
OSM UN DACE/E = Ferns having the young leaves cir- 
cinate, the spore-cases destitute of an elastic ring, and 
bursting vertically by two regular valves. It contains 
the genus Osmunda, 
17. Osmunda = Marginal-fruited Ferns, having the regu- 
lar-valved spore-cases in irregular, dense, branching 
clusters, terminating the fronds. 
