Family

Hymenophyllaceae

Nomenclature

Hymenophyllum exsertum Wall. ex Hook., Sp. Fil. 1: 109, t. 38A. 1844; Bedd., Handb. Ferns Brit. India: 30, f. 16. 1883; C.Chr., Contr. U.S. Natl. Herb. 26: 330, pl. 24. 1931; Copel., Philipp. J. Sci. 64: 153., pl. 83. 1937; Tardieu & C.Chr., Fl. Indo-Chine 7(2): 53; 1939 Holttum, Rev. Fl. Malaya ed. 1, 2: 86, f. 28. 1955 [‘1954’]; Holttum, Dansk Bot. Ark. 20: 17. 1961; Holttum, Dansk Bot. Ark. 23: 228. 1965; Tagawa & K.Iwats., Fl. Thailand 3: 611. 1989; Boonkerd & Pollawatn, Pterid. Thailand: 73. 2000. – Mecodium exsertum (Wall. ex Hook.) Copel., Philipp. J. Sci. 67: 23. 1938; Ching, Fl. Reipubl. Popularis Sin. 2: 136. 1959; Tagawa & K.Iwats., SouthE. Asian Stud. 5: 38. 1967; Tagawa & K.Iwats., Fl. Thailand 3: 73, f. 5.13. 1979.

Description

Rhizome wiry, hairy throughout, laxly branched, about 0.3 mm diam. Stipes remote, hairy on the abaxial side, (1.5–) 3–5 cm long, sometimes winged on the upper part. Laminae very variable in shape and size, oblong-ovate, oblong or oblong-lanceolate, round to acute at apex, bipinnatifid to tripinnatifid, (2–) 7–10 cm long, (1–) 2.5–4 cm wide; rachis like the upper part of stipes, hairy throughout, more densely on abaxial side, winged throughout by flat wings, wings of the upper part broader, to 0.8 mm on both sides; pinnae many, more than twelve in pairs on lower fronds, oblong to oblong-lanceolate, slightly falcate, round to moderately acute at apex, at most 2.5 cm long, 1 cm wide; pinnules with a few to several segments, in larger ones pinnately decompound; ultimate segments to 1.5 mm long, 1 mm broad, entire and flat; hairs on every axis, rather sparse on upper axis, brown, up to 2 mm long. Sori usually on upper side of pinnae, dispersing from near rachis outward, the base constricted; involucre bilabiate; lips subtriangular, moderately acute, entire and flat, to 2 mm long, 1 mm broad; receptacles clavate. Cell walls rather thick, coarsely pitted .

Distribution in Thailand

NORTHERN: Mae Hong Son, Chiang Mai, Chiang Rai, Lamphun, Phitsanulok; NORTH-EASTERN: Loei; SOUTH-WESTERN: Kanchanaburi, Phetchaburi; CENTRAL: Nakhon Nayok; SOUTH-EASTERN: Chanthaburi, Trat; PENINSULAR: Ranong, Krabi, Nakhon Si Thammarat, Trang.

Distribution in Laos

Champasak.

Distribution in Cambodia

Uncertain locality

Wider Distribution

N India, S China., Upper Burma, Indochina, south to Peninsular Malaysia.

Ecology

On mossy tree trunks in tropical evergreen forest at medium or higher altitudes.

Proposed IUCN Conservation Assessment

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

Voucher specimens - Thailand

Middleton et al. 4494 & 4898, Chiang Mai, Doi Inthanon National Park (E); Middleton et al. 5136, Loei, Phu Luang Wildlife Sanctuary (E); Middleton et al. 3293, Phetchaburi, Kaeng Krachan National Park (E).