THE BRITISH FERNS. 
WILSON'S FILM FERN. 
HYMENOPHYLLUM UNILATERALE. 
H. fronds pellueid-membranaceous, pinnate, elongate-oblong ; pin- 
nœ decurved, sub-unilaterally digitate-pinnatifid, slightly decurrent 
forming a narrow wing to the upper part of the rachis; segments 
linear, undivided or bifid, spinulosely serrate; involucres axillary, 
solitary, stalked, ovate, inflated, the valves entire. [Plate CIX.] 
HYMENOPHYLLUM UNILATERALE, Bory MS.: Willdenow, Sp. Plant. v. 521. 
Newman, Hist. Brit. Ferns, 3 ed. 301. Moore, Handb. Brit. Ferns, 3 ed. 
264; Id., Ferns of Gt. Brit. Nature Printed, t. 49 B. Sowerby, Ferns of 
Gt. Brit. 76, t. 43. Sprengel, Syst. Veg. iv. 133. Presl, Hymenophyll. 32. 
Hooker fil., Fl. New Zeal. ii. 11. Lowe, Nat. Hist. Ferns, viii. t. 6. 
HYMENOPHYLLUM WiLsoN1, Hooker, Brit. Fl. 1 ed. 450; Id., Sp. Fil. i. 95. 
Wilson, Supp. Eng. Bot. t. 9686. Hooker & Arnott, Brit. Fl. 7 ed. 592. 
Mackay, Fl. Hib. 345. Babington, Man. Brit. Bot. 4 ed. 428, Deakin, 
Plorigr. Brit. iv. 194, fig. 1617. Presi, Hymenophyll. 31. Nyman, Syll. 
Fl. Europ. 434. 
HYMENOPHYLLUM TUNBRIDGENSE, Schkuhr, Krypt. 134, t. 135 d (excl. syn.). 
HYMENOPHYLLUM TUNBRIDGENSE, B. Kunze, Linn. x. 555. Bentham, Handb. 
Brit. Fl. 638. 
HYMENOPHYLLUM PELTATUM, Desvaux, Prod. 833 ; according to Hooker. 
HYMENOPHYLLUM MENZIESII, Presl, Hy menophyll. 31, 51 ; according to Hooker. 
HYMENOPHYLLUM MEYERI, Presl, Hymenophyll. 31, 50 ; according to Hooker. 
TRICHOMANES PELTATUM, Poiret, Enc. Bot. viii. 76 ; according to Desvaux. 
TRICHOMANES TUNBRIDGENSE, Lightfoot, Fl. Scot. 681. Bolton, Fil. 58, t. 31. 
Caudex rigid, filiform, creeping, branched and forming dense 
entangled masses, dark brown, bearing a few hair-like scales about 
the bases of the fronds. Fibres slender, downy. 
Vernation circinate. 
Stipes slender, wiry, terete, one-third the length of the frond or 
often less; distant and lateral on the caudex, to which it is adherent. 
` Rachis terete below, narrowly-winged above. 
Fronds smooth, pellucid-membranaceous, minutely cellular, dark 
olivaceous green, from one or two to five or six inches long, oblong or 
linear 7. e. clongate-oblong, pinnate. Pinne decurrent in the upper 

