Family

Pteridaceae, subfamily Pteridoideae

Nomenclature

Pityrogramma calomelanos (L.) Link, Handbuch 3: 20. 1833; Tardieu & C.Chr., Fl. Indo-Chine 7(2): 189, f. 22.3 & 22.4. 1940; Holttum, Rev. Fl. Malaya ed. 1, 2: 593, f. 348. 1955 [‘1954’]; Holttum, Dansk Bot. Ark 20: 33. 1961; Holttum, Dansk Bot. Ark 23: 243. 1965; Tagawa & K.Iwats., SouthE. Asian Stud. 3(3): 88. 1965; Tagawa & K.Iwats., SouthE. Asian Stud. 5: 109. 1967; Tagawa & K.Iwats., Acta Phytotax. Geobot. 23: 56. 1968; Tagawa & K.Iwats., Fl. Thailand 3: 193. 1985; Boonkerd & Pollawatn, Pterid. Thailand: 103, 124. 2000. – Acrostichum calomelanos L., Sp. Pl. 1072. 1753. – Pellaea calomelanos (L.) Link, Fil. Spec.: 61. 1841; Bedd., Handb. Ferns Brit. India: 104. 1883.

Description

Rhizome short, erect, bearing a tuft of fronds, covered with scales; scales bright brown, narrow, 3–6 mm long, thin, entire. Stipes up to 30 cm long, dark purple, polished, scaly on lower part, glabrous upwards, covered with white powder in young stage. Laminae oblong, with acuminate apex, bipinnate-tripinnatifid, 15–30 by 8–15 cm; rachis grooved on upper surface; lateral pinnae gradually smaller upwards; lower ones stalked, linear-subtriangular, acuminate to long-tailed at apex, up to 10 by 2.5 cm; pinna-rachis slender, grooved; grooves decurrent to those on rachis; pinnules oblong to oblong-lanceolate, cuneate at base, acute to acuminate at apex, lobed or pinnatisect in larger ones, up to 1.5 by 1 cm; lobes oblanceolate to spathulate, acute and dentate at apical portion, herbaceous, light green, glabrous but coated with white waxy powder; veins free, pinnate in larger ones, to several times forked. Sporangia placed along veins throughout the lower surface, without any protection.

Distribution in Thailand

NORTHERN: Mae Hong Son, Chiang Mai, Tak; SOUTH-WESTERN: Kanchanaburi, Prachuap Khiri Khan; SOUTH-EASTERN: Trat; PENINSULAR: Nakhon Si Thammarat, Phangnga, Trang, Satun, Yala, Narathiwat.

Distribution in Laos

Khammouane.

Distribution in Cambodia

Kampot.

Wider Distribution

Pantropics; this may have been spread to the palaeotropics by humans.

Ecology

On open mountain slopes in recently felled areas or along new roads at low or medium altitudes.

Proposed IUCN Conservation Assessment

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

Notes

The white powdery covering of the lower surface of fronds is a distinct feature of this species. It is cultivated widely as silver fern and the Asiatic plants are usually considered as those naturalized from cultivation.

Voucher specimens - Thailand

Middleton et al. 4746, Kanchanaburi, Khao Laem National Park (E).

Voucher specimens - Laos

Delacour s.n., Khammouane, Nape (P).

Voucher specimens - Cambodia

Poilane 23058 & 23071, Kampot, Bokor (P).