Family

Pteridaceae, subfamily Pteridoideae

Nomenclature

Pteris mertensioides Willd., Sp. Pl.: 5: 394. 1810; Holttum, Rev. Fl. Malaya ed. 1, 2: 404. 1955 [‘1954’]; Tagawa & K.Iwats., SouthE. Asian Stud. 5: 81. 1967; Tagawa & K.Iwats., Fl. Thailand 3: 244, f. 19.1. 1985; Boonkerd & Pollawatn, Pterid. Thailand: 129. 2000.

Pteris patens Hook., Sp. Fil. 2: 177, t. 137. 1858, non Kunze 1837: Bedd., Handb. Ferns Brit. India, 114, f. 59. 1883.

Description

Rhizome short, ascending, scaly; scales up to 10 by 0.5 mm, dark brown, more or less waved and curled up, sharply toothed at margin. Stipes stout, densely scaly and warty at base, puberulous or glabrescent upwards, up to 119 cm in length. Laminae up to 137 cm or more long, 65 cm wide, deeply bipinnatisect to bipinnate; lateral pinnae nearly opposite, up to 16 pairs, linear-lanceolate, up to 45 by 4–8 cm, basal pinnae bearing large basiscopic pinnules; rachis and costa castaneous to purplish, grooved on upper surface, hairy beneath; pinnules lanceolate, moderately acute to acute at apex, adnate at base decurrent to the next ones with wings of costa less than 1 mm broad, or free in larger ones, up to 50 by 7 mm, papyraceous to softly chartaceous, green; veins usually twice forked, distinct on both surfaces. Sori continuous nearly all the margin of pinnules except at apex and sinus; indusia narrow, pale, thin.

Distribution in Thailand

SOUTH-WESTERN: Phetchaburi; PENINSULAR: Chumphon, Ranong, Surat Thani, Nakhon Si Thammarat, Satun, Yala.

Wider Distribution

Sri Lanka, S India, Malesia to Polynesia.

Ecology

On damp slopes in tropical evergreen forests at low to medium altitudes.

Proposed IUCN Conservation Assessment

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

Voucher specimens - Thailand

Middleton et al. 4794, Phetchaburi, Kaeng Krachan National Park (E); Middleton et al. 5348, Satun, Thale Ban National Park (E).