Hydnophytum hellwigii Warb.

42. Hydnophytum hellwigii Warb. View in CoL — Fig. 45 View Fig ; Map 6 View Map 6

Hydnophytum hellwigii Warb. (1894) 209. — Type: Hellwig 469 (Lectotype selected here B presumed lost). Epitype selected here, Gillison & Streimann 25662 ( K; isoepitypes A, BO, BRI, CANB, L, LAE, SING), Papua New Guinea, Morobe Province, Buso River , 16 Aug. 1968.

Hydnophytum parvifolium Valeton (1927) 140. — Type: Schlechter 19405 (lectotype selected here K; iso F, G, L), Papua New Guinea, Morobe Province, Waria River, Pema, 11 May 1909, syn. nov.

Hydnophytum punamense Lauterb. in K.Schum. & Lauterb. (1905) 401; Valeton (1911) 508; (1927) 140; Merr. & L.M.Perry (1945) 23. — Type: Schlechter 14671 (WRSL), Papua New Guinea, New Ireland, Punam, June 1902, syn. nov.

Tuber globose, to 20 cm, regular, smooth. Entrance holes numerous, conical with narrow rims, 0.3–0.6 cm diam. Cavities small. Stems several, branching, pendulous to erect, quadrangular in section, with 4 narrow ridges. Internodes 0.5–6 by 0.05–0.3 cm. Leaves sessile to barely petiolate, distichous. Lamina linear-ovate; 3 by 0.7 to 6.2 by 2.4 cm; apex acute, but blunt at its extremity; base rounded; midrib prominent below, veins 4–6; thin, mid-green. Petiole to 0.4 cm; stipules triangular, papery to 0.2 cm, ± persistent. Inflorescence paired, sessile. Bracts inconspicuous, <1 mm. Flowers [4] not heterostylous. Calyx to 1 mm. Corolla tube to 1 mm, lobes to 0.5 mm, with a minute ring of hairs within mouth of tube. Anthers 0.3 mm, partly exserted. Pollen colporate, 36 (30–41) μm, brochi 1 μm. Stigma 2-lobed, reaching to top of anthers. Fruit 4 by 2 mm, red. Pyrenes ellipsoid to ovoid, 3 by 2 mm; apex rounded to acute; base rounded.

Ecology & Habitat — A coastal species, forest, from sea level to 600 m (once at 1 800 m). Tuber only occasionally not inhabited by ants.

Distribution — Papua New Guinea and the Solomon Islands.

Conservation status — Least Concern (LC). Whilst probably Vulnerable in some parts of its range, this taxon is spread across 1 400 km with herbarium collections indicating at least 12 locations (subpopulations). Other information: georeferenced collections 15, EOO c. 510 000 km 2.

Notes — This species has delicate, long-ovate leaves, which taper into an ultimately rounded apex. The stems are slender, and the leaves are usually disposed at right angles to the stem in a strikingly distichous manner for the genus. The north coast specimens, especially those from the Bismarck Archipelago and Milne Bay Province, as well as those from the coasts of Madang and Morobe Province are all fairly uniform. However, a number of collections from Southern Highlands and Gulf Province have been provisionally included here, and these may represent separate taxa ( Map 6 View Map 6 ). Clemens 11094 from Wantoat has a more lanceolate, thicker leaf, while Carr 13963 from Northern Province has exceptionally long leaves compared to other collections from the same area. Of the five collections from the Southern Highlands and Gulf Provinces, Gray & Floyd NGF 8026 has large elliptic leaf blades, while the others all have smaller, cordate-elliptic blades. All these specimens share stem and inflorescence characters as well as the delicate leaf texture of the north coast specimens. A map of leaf outlines is presented in Map 6 View Map 6 .

There are no recent collections from Finschhafen, and we have decided not to neotypify this species, since collections from the type locality could be readily made. In the meantime, we have adopted an epitype to serve as a discriminating element until such time as suitable topotype material becomes available.