Hydnophytum magnirubrum Jebb & C.R.Huxley, 2019

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 : 68-69

37. Hydnophytum magnirubrum Jebb & C.R.Huxley , sp. nov. — Fig. 40

Tuber globosum , superficie laevi. Aperturae duo generum, vel infundibuliformes, ad 4 cm in diametro, vel parvae et conicae, ad 0.5 cm in diametro. Tuberis contextus badius. Caules numerosi, libere ramosi. Lamina elliptica usque obovoidea, 3 per 1.4 ad 6 per 3 cm, apice rotundato usque acuto, basi sensim attenuata. Petiolus ad 0.3 cm. Inflorescentia sessilis, binata, bracteis obtecta; quae bracteae papyraceae usque coreaceae, ad 0.5 cm. Calyx ad 3.5 mm, margine irregulariter dentato. Corollae tubus ad 10 mm, albus, intus pilis conspersus. Lobi ad 5 mm, rubello-purpurei. Antherae ad 1.5 mm, exsertae ex fauce corollae. Stigma 3-lobatum. Pyrenae (2–)3(–4), hemisphericae usque obovoideae, 3 per 2 mm.

— Typus: Jebb 261 (holo LAE; iso A, BRI, CANB, K, L), Papua New Guinea, S6°07' E143°57', SE of Mt Giluwe , above Onin , ‘ Beechwoods No. 2’ logging track , 23 Apr. 1983 .

Etymology. There are two taxa in Papua New Guinea with red tuber tissue and red-tipped corollas, of the two this has the larger leaves.

Tuber globose, to 30 by 19 cm; surface smooth, grey. Entrance holes of two kinds, some conical, or lipped, to 0.5 cm diam; others more numerous and funnel-like, to 4 cm diam. Cavity walls partly silver-grey in colour, partly purplish brown. Tuber tissue reddish brown. Stems numerous, to 100 by 0.8 cm, freely branching, spreading and upcurving. Internodes to 7 by 0.8 cm when sterile, 0.4–3 by 0.2–0.4 cm when fertile. Leaves erect to spreading. Lamina , elliptic to obovoid; 3 by 1.4 to 6 by 3 cm; apex rounded to acute; base shortly-attenuate; sclerophyllous, dark green, glossy above, pale below; margin downcurved; veins 5–7; midrib prominent below, pale yellow. Petiole to 0.3 cm, rounded, yellow to reddish in colour; stipules 0.2–0.3 cm, triangular, with a central process, caducous. Inflorescence paired, sessile, bract-covered, these papery to leathery, to 0.5 cm. Flowers [7] incompletely heterostylous. Calyx to 3.5 mm, margin irregularly toothed. Corolla tube to 10 mm, white; lobes to 5 mm, with a crest at apex, reddish purple; with scattered hairs within. Anthers to 1.5 mm, just exserted from corolla mouth. Pollen 94 (73–120) μm, 3-colpate, brochi irregular, 1–2.5 μm, vesicles small. Stigma 3-lobed at or barely above level of anthers, or exserted. Fruit globose, to 5 mm, red. Pyrenes (2–)3(–4), hemispherical to obovoid, then triangular in section, 3 by 2 mm.

Ecology & Habitat — Mid- to high-level epiphyte in Nothofagus forest, 2 400–2 800 m. Tuber cavities not inhabited by ants, instead occupied by spiders, myriopods and other arthropods.

Distribution — Papua New Guinea (Enga and Southern Highlands Provinces).

Conservation status — Endangered (EN) under criteria B1ab (iii)+2ab(iii). The four known localities lie within 100 km of one another. Other information:AOO 365 km 2 (using an auto-value cell width of 10 km), EOO 2 500 km 2.

Additional specimens examined. Jebb 300 (BRI, K, L, LAE ), Enga Province: S5°36' E143°30', Kandep Pass, on road from Laiagam; Huxley & Turton in UPNG 5919B (A, UPNG), Southern Highlands Province, S5°57' E143°51', NW Foothills of Mt Giluwe, on Mendi-Hagen Road; Jebb 264 (L), 265 (K), 266 ( LAE ), 269 ( LAE ), 270 (K), 273 (L), 274 (A, BRI), 276 ( LAE ), 277 (CANB, LAE ), 278 (A), 279 ( LAE, UPNG ), 281 ( LAE ), 282 ( LAE ), 285 ( LAE ), 286 ( LAE, SUVA ), Ash UPNG 3467 (BRI, CANB, LAE, UPNG ), Ash UPNG 3468 (UPNG), Ash UPNG 3475 (UPNG), Schodde 1701 (L,A),S6°07' E143°57', SE of Mt Giluwe, above Onin, ‘Beechwoods No. 2’ logging track; NGF 28276 ( LAE ), Mt Ambua.

Note — This species is closely related to H. minirubrum [35] with which it is sympatric, and to H. archboldianum [33].

Figures

Fig. 40 Hydnophytum magnirubrum Jebb & C.R.Huxley. a. Shoot; b. flower; c. pyrene adaxial face;d. lateral view (a: Jebb 300; b, c: Jebb 278). — Scale bars: a = 10 cm; b–d = 10 mm. — Drawn by Rosemary Wise.