Etymology

According to Holttum (1954), the botanical name, Adiantum (unwetted) refers to the way in which water-drops run off the surface of the pinnae without wetting them.

Family

Pteridaceae, subfamily Vittarioideae

Nomenclature

Adiantum gomphophyllum Baker, Ann. Bot. (Oxford) 8: 124. 1894. – Type: Thailand, Phangnga, Curtis 2958 (K; possibly unnumbered isotype E).

Description

Lithophytic. Rhizome short, erect, covered with scales; scales narrow, black with a pale brown margin, 1.5–2.5 mm long, 0.1–0.2 mm wide, margin entire. Stipe dark brown, 1–5 cm long, glabrous or with a few scales near base. Laminae simply pinnate, 6–30 cm long, 1.4–3.1 cm wide, oblong in outline; rachis glabrous; pinnae 6–22 on each side of rachis, gradually becoming slightly smaller upwards; pinnae on stalks 2–3 mm long; pinnae flabellate, sometimes with the lower margin slightly longer, 9–14 by 6–14 mm, base cuneate, margins entire and straight or with lower margin weakly sinuate, flat apex with a narrow and shallow sinus in some pinnae, thin, glabrous above and beneath; veins dichotomous, slightly raised above; stipe, rachis and pinnae stalks persistent. Sori on flat apex of lobes, 2–5, elongate , 1–1.5 mm long.

Distribution in Thailand

PENINSULAR: Phangnga, Satun.

Wider Distribution

Endemic to Thailand.

Ecology

In crevices of limestone cliffs in forest at low altitude.

Similar species

Adiantum phanomensis S.Linds. & D.J.Middleton

Proposed IUCN Conservation Assessment

Vulnerable B1ab(ii)(iii). This species is confined to karst limestone, a habitat that is often exploited for cement production or degraded due to fire in surrounded farmland or recreational use.  Although the exact Extent of Occurrence is unknown it is clearly is less than 20,000 km2, justifying a vulnerable category.

Voucher specimens - Thailand

Middleton et al. 5363, Satun, Phu Pha Phet Cave area (E); Middleton et al. 5426, Phangnga, Tham Pha Phueng (E).