Pteris mertensioides Willd.
Pteridaceae, subfamily Pteridoideae
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.
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.
Sri Lanka, S India, Malesia to Polynesia.
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).
Basal pinnae with enlarged basiscopic pinnules
Upper surface of pinnae
Upper surface of pinna
Lower surface of rachis and bases of pinnae
Pinnules and sori
Pinnules and sori
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