5% HISTORY OF BRITISH TERNS. 



14. Woodsia = Dorsal-fruited Ferns, having the indusia 



involucriform, i.e. attached beneath the sori, and 

 divided at the margin into hair-like incurved seg- 

 ments. 



§ HYMENOPHYLLEjE = Fenis whose sori arepi'O- 

 duced around the ends of teins projecting from the 

 margin, and surrounded by urn-shaped or tivo-vaked 

 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 = IMarginal-fruitcd Ferns, having 



the sori surrounded by two-valved expansions of the 

 frond. 



OSMUNDACE/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 = Mardnal-fruited Ferns, having the regu- 



lar-valved spore-cases in irregular, dense, branching 

 clusters, terminating the fronds. 



