458 FILICES. [HYMENOPHYLLUM. 



Involucre hooded, on one side of the sorus 10. Cystopteris. 



Involucre orbicular, peltate, superior 11. Aspidium. 



Involucre reniform, superior 12. Nephrodium. 



**** Sori dorsal ; involucre (see Ceterach under Asplenium). 



Sori globose or oblong 13. Polypodium. 



Sori linear 14. Gymnogramme. 



TKIBE III. OSMUN'DE-ffl. Frond coriaceous or membranous. Involucre 0. 

 Capsules sessile or shortly stalked, vertically 2-valved, with a short lateral 



or subterminal striate areola. Vernation, circinate 15. Osmuuda. 



TRIBE IV. OPHIOGLOS'SE^E. Capsules large, 2-valved, without a ring or 

 areola, coriaceous, in spikes or panicles. Vernation straight. 



Frond ovate, simple. Capsules spiked 16. Ophioglossum. 



Frond pinnate. Capsules panicled 17. Botrychium. 



1. HYMENOPHYJjLUM, Sm. FlLMY-FERN. 



Rootstock filiform or capillary, creeping. Fronds usually matted and 

 2-4-pinnatifid or -pinnate, pellucid, reticulate ; segments with a midrib ; 

 veins 0. Sori marginal, axillary or terminal ; involucre free or sunk in 

 the frond, 2-valved or 2-lipped, opening outwards ; capsules sessile on a 

 columnar receptacle ; ring complete, oblique. DISTRIB. Chiefly trop. and 

 S. temp, regions ; species 70. ETYM. v^v and <t>v\\ov, from the mem- 

 branous fronds. 



1. H. tunbridgen'se, Sm. ; frond ovate pinnate below pinnatifid 

 above, pinnae spreading spinulose-serrate, lips of involucre toothed. 

 Moist shaded rocks or copses, from Mull and Argyle southwards, and in Ire- 

 land, rare ; Channel Is. ; ascends to 1,000 ft. in Cornwall ; frt. June-July. 

 Rootstocks capillary, interlaced. Stipes 1-2 in., winged above. Frond 1-3'm., 

 glabrous ; pinnae distichous, flabellately piunatifid, lobes linear ; involucre 

 solitary, axillary, suborbicular, lips strongly irregularly toothed. DISTRIB. 

 Belgium, France, Germany, Italy, Canaries, S. temp, regions. 



2. H. unilaterale, Willd.; frond oblong pinnate below or throughout, 

 pinnules decurved spiuulose-serrate, lips of involucre entire. //. Wiltumi, 

 Hook. 



Shaded rocks and copses, extending to Orkney and Shetland, and in Ireland ; 

 ascending to 2,800 ft. in the Hebrides ; frt. June-July. Very near //. /,<- 

 bridfjense, and perhaps only a sub-species, but more rigid, darker green ; 

 involucre more ovoid and turgid ; pinnae pinnatifid chiefly on the upper 

 side. DISTRIB. As H. tutibridgense. 



2. TRICHOM ANES, L. BRISTLE-FERN. 



Rootstock creeping or tufted, stout or slender. Fronds erect or pendu- 

 lous, simple pinnate or 1-4-pinnatifid, usually pellucid, reticulate ; 

 segments with 1 stout simple or forked midrib. Sort marginal, axile or 

 terminal ; involucre elongate, free or sunk in the frond, tubular or cam- 

 panulate, mouth entire, or 2-lipped, opening outwards ; capsules sessile 

 on a long often exserted receptacle. DISTRIB. Chiefly trop. and damp 

 warm climates ; species 78. ETYM. Obscure. 



1. T. rad leans, Sw. ; rootstock creeping, frond 2-3-pinnatifid. 

 Wet shaded rocks, S. and S.W. of Ireland, local ; formerly at Bingley, York- 



