Family

Hymenophyllaceae

Nomenclature

Hymenophyllum riukiuense Christ, Ann. Cons. Jard. Bot. Genève 4: 208. 1900; Copel., Philipp. J. Sci. 64: 123, pl. 61. 1937; Tagawa & K.Iwats., Fl. Thailand 3: 611. 1989. – Mecodium riukiuense (Christ) Copel., Philipp. J. Sci. 67: 21. 1938; Tagawa & K.Iwats., SouthE. Asian Stud. 5: 38: 1967; Tagawa & K.Iwats., Fl. Thailand 3: 72, f. 5.2. 1979; Boonkerd & Pollawatn, Pterid. Thailand: 75. 2000.

Description

Rhizome less than 0.2 mm diam., lax1y branched, the rootlets densely hairy. Stipes dark, glabrous, 1–2 cm long, slender, winged throughout with crispate wings up to 0.6 mm wide on one side. Laminae oblong to oblong-subdeltoid, acute at apex, tripinnate to quadripinnatifid, herbaceous, green to dark green, glabrous, 2–4 cm long, 1–3 cm wide at basal widest portion; pinnae five or more in pairs, the basal ones triangular-rhomboid to oblong with a few pinnules, round at apex, cuneate at base, upper ones gradually becoming smaller; rachis like the upper parts of stipes, slender, somewhat zigzag, winged throughout; ultimate segments narrowly lanceolate, entire but more or less waved at margin, obtuse to retuse at apex, 0.6–1 mm broad, longer ones more than 4 mm long, the base decurrent to form the crispate wings of every axis. Sori usually aggregated at the apical part of frond; involucre bilabiate, 0.8–1.3 mm long, longer than wide, the lips toothed to fimbriate; receptacles columnar. Cell walls thin and entire .

Distribution in Thailand

NORTH-EASTERN: Loei.

Wider Distribution

Southern edge of Japan to the Ryukyus.

Proposed IUCN Conservation Assessment

Least Concern (LC). This species is widespread and not under any immediate known threat.