Hydnophytum angustifolium Merr.

Jebb, M. H. P. & Huxley, C. R., 2019, The tuberous epiphytes of the Rubiaceae 7: a revision of the genus Hydnophytum, Blumea 64, pp. 23-91 : 85

a. Hydnophytum angustifolium Merr.

Hydnophytum angustifolium Merr. (1908) 162. — Types: Clemens s.n., May, June 1907, April 1906 (PNH not seen, presumed lost), Philippines, Mindanao, Lake Lanao, Camp Keithly; Copeland s.n., March 1905 (PNH not seen, presumed lost),Philippines,District of Zamboanga, San Ramon, March 1905.

Description taken from Merrill (1908): “ Tuber irregular, at least 15 cm diameter, brown or greyish, unarmed. Stems several, diffusely branched, slender at least 60 cm long grey or brown, the branches elongate, brown furfuraceous and angled when young. Leaves lanceolate or narrow-lanceolate, 5 by 0.6 to 10 by 1.8 cm, base and apex gradually narrowed, tip acute or blunt; midrib prominent beneath, lateral veins obscure, leathery; pale green when dry, somewhat shining. Petiole ± absent. Inflorescence slightly raised. Calyx 1 mm, truncate. Corolla 2 mm, slight ring of hairs at the middle. Anthers 0.7 mm. Style 1.2 mm. Fruit to 10 mm long, about 4 mm wide at base gradually narrowed upwards, red, somewhat fleshy.”

Ecology & Habitat — Unknown.

Distribution — Philippines (Mindanao).

Note — Originally distinguished by its narrow leaves and elongate fruits. We have seen none of the material mentioned by Merrill, which may be lost, and are therefore unable to give a view of the tenability of this species with regard to H. moseleyanum [14], H. formicarum [1] or most especially H. puffii [2]. The taxon appears to differ from the latter species in the combination of furfuraceous twigs, obscure secondary veins, a sparse ring of hairs in the corolla and a narrow fruit. Satellite imagery suggests that forest still survives near the type locality so recollecting the taxon would probably be feasible.