HYMENOPHYLLACEAE Hymenophyllum Sm.

XV. HYMENOPHYLLACEAE View in CoL 1

Plants small. Rhizomes slender, extensively creeping. Lamina dark, translucent green, only one cell thick except on the veins. Sori gradate, marginal; indusium tubular or 2-valved, symmetrical; spores tetrahedral.

A predominantly austral and tropical family. Delimitation of species is difficult, and the plants from Europe are held by some authors to be conspecific with those in the tropics or the Southern hemisphere; but they are, as here delimited, believed to extend outside Europe only to the Atlantic Islands (Madeira and Canarias).

Literature: E. B. Copeland, Philipp . Jour. Sei. (Bot.) 67: 1 (1938). Rhizome filiform; indusium of 2 distinct valves; receptacle included 1. Hymenophyllum

Rhizome 2-4 mm in diameter; indusium tubular; receptacle exserted 2. Trichomanes

1. Hymenophyllum Sm. 1

Very small, with the habit of bryophytes, and often growing with them. Rhizomes filiform, less than 1 mm in diameter, smooth. Leaves more or less procumbent, persistent after withering, forming a dense mat of foliage, deeply pinnatisect, the segments asymmetrical, subentire on their proximal side, deeply lobed on their distal side with 2-15 oblong, obtuse, dentate lobes. Sori solitary, more or less globose, situated near the base of the distal segments of the frond; indusium of 2 ovate or suborbicular valves, united only at the base.

Literature: E. B. Copeland, Philipp . Jour.Sci. (Bot.) 64: 1 (1937).

Valves of indusium dentate; leaves bluish-green 1. tunbrigense

Valves of indusium entire; leaves somewhat olive-green 2. wilsonii

1. H. tunbrigense (L.) Sm. View in CoL in Sowerby, Engl. Bot. 3; t. 162 (1794).

Lamina usually 22-45 x c. 15 mm, flat, of a somewhat glossy, slightly bluish-green. Indusium-valves suborbicular, fimbriate-dentate in distal half, nearly flat. 2« = 26. Woods and other damp, shady, shelteredplaces. Locally in W. Europe from the Pyrenees to Scotland; Açores; isolated stations in N. Italy and E. Germany. Az Be Br?Co Ga Ge Hb Hs It?Ju.

2. H. wilsonii Hooker View in CoL , Brit. FI. 450 (1830)

( H. unilaterale auct., vix Bory).

Like 1 but with usually narrower leaves, which are deflexed laterally and therefore appear even narrower, of a darker, somewhat olive-green. Indusium-valves ovate, entire, convex. 2« = 36. Similar situations to 1 but more tolerant of exposure. N. W. Europe; Açores. Az Br Fa Ga Hb No.