IV.] 



FILICES. 



349 



{b.) Annulus oblique, transverse, incomplete or cap-like, 

 Ceratoptcris. — An aquatic Fern, with distinct sterile and 

 fertile fronds. Sori continuous along the veins of the 

 narrow lobes of the fertile fronds. Indusium formed by 

 the revolute margins of the lobes. Annulus of the sporanges 

 incomplete. Spores marked with three separate series of 

 concentric rings. 



Hymenophyllu77i, — Sori at the end of veins, terminating 

 lobes of the frond. Sporanges with a horizontal annulus, 

 sessile upon a slender column within a two-valved indusium. 

 The fronds of this genus and the following are half-pellucid. 

 They are often very small and the rhizome is densely 

 matted. 



Fig, 232. Pinnule and sorus ol 



HymeTtophylhan. 



Fig. 233. Pinnule and sorus of 

 Trichoittanes. 



Trichoma7ies. — Sori and sporanges as in HymeTiophylhwt. 

 The indusium tubular, and the hair-like column projecting 

 beyond it, the sporanges clustered near its base. 



Gleichenia {dichotoma). — Sori scattered, of few sessile 

 sporanges. Sporanges opening vertically with a transverse 

 ring. Indusium o. 



Lygodiwn. — Slender, climbing Ferns with pinnate fronds. 

 Sporanges on the under side of marginal or terminal lobes 



