Hydnophytum ellipticum Merr. & L.M.Perry

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 : 38-39

7. Hydnophytum ellipticum Merr. & L.M.Perry — Fig. 8 ; Map 2

Hydnophytum ellipticum Merr. & L.M.Perry (1945) 19. — Type: Brass 12111 (A), New Guinea, West Papua Province , 15 km southwest of Bernhard Camp, Idenburg River , Jan. 1939 .

Tuber irregularly globose, 10–22 cm across. Entrance holes numerous, of two types: the majority prominently lipped (to 0.6 mm tall), 0.15–0.8 cm diam, others fewer, funnel-like, and then 0.9–2 cm across. Roots numerous, scattered on surface, 0.1–1 cm long. Cavities largest in centre, spiral in structure, to 5 cm diam. Warts absent from all cavity walls. Stems several, upcurved, branching, to 40 by 0.4 cm; young stems ferruginous; internodes 3–5 cm, rounded to angular; nodes swollen, 1 cm or more across. Lamina lanceolate-elliptic; 4.8 by 1.9 to 8 by 4.3 cm; apex acute to acuminate, ultimately blunt; base attenuate; leathery; midrib prominent above and below; veins 4–8. Petiole 0.3–0.8 cm; stipules minute, caducous. Inflorescence sunken, cup-like alveoli, 0.5–0.7 cm across, with a prominent rim, filled with a dense cushion of hairy bracts to 0.4 cm, and papery bract remains. Bracts persistent on old stems. Flowers [3] heterostylous. Calyx entire to 1 mm, sometimes with bract hairs attached. Corolla tube to 7.5 mm; lobes 2.5 mm; with a broad ring of hairs at mouth of tube and extending to insides of lobes, hairs to 1.6 mm. Short-styled flowers with anthers to 2 mm; exserted on filaments 1 mm long; pollen 41 (38–43) µm across, brochi 1–2 µm; stigma 2-fid, below mouth of tube. Long-styled flowers with anthers to 1.5 mm, within mouth of tube; pollen 51 (49–52) µm across, brochi very fine; stigma, exserted. Fruit 6.5 by 3 mm. Pyrenes broad-obovoid 3.5 by 2.7 mm; apex rounded truncate, with a blunt apiculus; base tapered; abaxial side with a longitudinal ridge.

Ecology & Habitat — Forest, (? 80–)1070–1840 m. Tuber not inhabited by ants.

Distribution — Indonesia (western New Guinea), Papua New Guinea.

Conservation status — Least Concern (LC). Whilst probably Vulnerable in some parts of its range, this taxon is widespread across much of central New Guinea with herbarium collections indicating 7 locations (subpopulations). Other information: georeferenced collections 8, AOO 17 500 km 2 (using an auto-value cell width of 50 km), EOO c. 58 000 km 2.

Notes — Beccari records a H. ellipticum in Blume’s herbarium, which he synonymised with H. formicarum blumei (Beccari 1885: 64). Since no description was given, and no specimen has been traced, we feel it unnecessary to qualify the Merrill and Perry name as a homonym.

A distinctive species with its slender stems and relatively large swollen nodes with pulvinate bract cushions. The leaves are lanceolate and have a midrib prominent above and below. It can be distinguished from the H. petiolatum complex [11] by the more lanceolate leaves (although these are approached by H. petiolatum var. nigrescens [11g]), and the generally higher altitudes occupied by the present species. Pulle 307 reputedly comes from low altitude (80 m), and although this may be correct, it is also possible that the measure represents camp data rather than the actual collection site.

Figures

Map 2 Distribution map of Hydnophytum ellipticum Merr. & L.M.Perry (●), H. lauterbachii Valeton (◆), H. magnifolium Merr. & L.M.Perry (*).

Fig. 8 Hydnophytum ellipticum Merr. & L.M.Perry. a. Shoot; b. leaf, c. half flower; d. pyrene abaxial face (Jebb 429 (LAE), Southern Highlands: S6°38' E143°51', 3 km SW of Erave on path to Samberigi). — Scale bars: a, b = 5 cm; c, d = 5 mm. — Drawn by Rosemary Wise.