Hydnophytum terrestris Jebb & C.R.Huxley, 2019

35. Hydnophytum terrestris Jebb & C.R.Huxley View in CoL , sp. nov. — Fig. 38 View Fig ; Map 5 View Map 5

Saepe terrestre. Tuber irregulariter globosum. Caules numerosi, ramosi. Internodia 4-angulata, alata. Lamina lanceolata usque ovata, latissima ad tertiam partem longitudinis, 3.5 per 1 ad 11 per 4 cm, apice sensim attenuato usque acuminato, basi abrupte angustata. Petiolus ad 1 cm. Stipulae grandes, triangulares, obtusae, ad 1 cm. Inflorescentia binata sessilis, raro quadruplex, tandem pedunculata. Bracteae densae, inflorescentiam obtegentes, triangulares, ad 0.8 cm. Flores heterostyli. Calyx ad 1.5 mm. Corollae tubus ad 4.5 mm, lato annulo pilorum instructus; lobi ovati, ad 4.5 per 2 mm.Antherae ad 1 mm. Stigma 2-fidum.Fructus ellipsoideus.Pyrenae complanatae, ellipsoideae.

— Typus: Kairo 459 (holo LAE; iso A, Bulolo , CBG, K, L, UPNG), Papua New Guinea, Lufa , track to Mt Michael , S6°21’ E145°17’, 5 km SW of Lufa .

Etymology. For the unusual terrestrial nature of the species.

Epiphytic or terrestrial. Tuber globose, highly irregular in outline when growing terrestrially or beneath leaf litter, more regular when epiphytic, to 25 by 30 cm, pale brown. Entrance holes numerous, prominent, conical, 0.3–1 cm across. Cavity surfaces pale brown, warted at extremities. Tuber tissue white. Stems numerous, branching, erect, to 1 m, rarely with tuberous swellings with cavities, particularly when stems lie beneath leaf litter; internodes to 10 cm or more near tuber, becoming more condensed when fertile, 4-angled, winged immediately below nodes, wings running from between the petiole bases largest. Leaves squarrose, stiff, leathery. Lamina ovate to lanceolate, widest at 1/3 length; 3.5 by 1 to 11 by 4 cm; apex tapering to acuminate; base narrowing abruptly. Dark glossy green above, paler below; drying grey-green with purple markings in herbarium specimens. Petiole to 1 cm; stipules large, triangular, blunt, to 1 cm, with a prominent wing, caducous. Inflorescence sessile, paired, rarely 4, becoming pedunculate. Bracts dense, covering inflorescence, triangular, to 0.8 cm, keeled, papery; drying grey/brown, persistent. Flowers [7] heterostylous. Calyx to 1.5 mm, entire, dentate or minutely ciliate. Corolla tube to 4.5 mm, widest at middle; with a broad ring (2 mm) of hairs at mouth, exserted in open flower; lobes ovate, to 4.5 by 2 mm, uncus <1 mm. Short-styled flowers with anthers to 1 mm, filaments to 1.5 mm; pollen 3-colporate, 42–54 μm, walls to 2.5 μm, colpi to 35 μm long, 7 μm wide, brochi to 1 μm; stigma 2-fid, immediately within mouth of tube. Long-styled flowers with anthers at mouth of tube; filament <0.5 mm; pollen 35–42 μm diam; stigma exserted. Fruit ellipsoid, to 6 by 3 mm. Pyrenes flattened, ellipsoid, 3.8 by 2.2 mm; apex and base rounded.

Ecology & Habitat — A low-level epiphyte, regularly becoming terrestrial by falling from tree, becoming buried in leaf litter, and then appearing as a shrub. Often growing at the very base of tree trunks. Tuber sometimes deeply buried, with upper surface 5–10 cm below surface. In Castanopsis - Nothofagus forest, 1 800–2 100 m. Abundant around Mt Michael. Tuber inhabited by a range of ant species.

Distribution — Papua New Guinea (Eastern Highlands Province).

Conservation status — Critically Endangered (CR) under criteria B1ab(iii)+2ab(iii). The collections indicate just 3 locations within a range of 20 km. This taxon is confined to lower montane forests around Mt Michael, a habitat that probably comprises less than 40 km 2 in total area. Other information: AOO 8 km 2 (using an auto-value cell width of 3 km), EOO 15 km 2.

Additional specimens examined. Jebb 101 ( LAE ), Jebb 328 ( LAE ), Jebb 329 (K, L), Jebb 330 ( LAE ), Jebb 331 ( LAE ), Jebb 332 ( LAE ), S6°21' E145°16',Eastern Highlands Province, just past Duto,on road beyond Lufa, Mt Michael, Lufa subdistrict,12 May 1983; Jebb 311 ( LAE ), Jebb 312 ( LAE ), Jebb 313 ( LAE ), Jebb 314 (BRI, K, L), Jebb 315 ( LAE ), S6°28' E145°26', SW of Lufa, on logging track in the Frigano Timber Lease, Habu river, Lufa subdistrict, 11 May 1983; Brass 31377 (A, L), Mt Michael, NE slopes; Jebb 123 ( LAE ), Lamari valley.

Note — The name refers to the unique habit of this species being found at the base of trees, or with its tuber buried in the leaf litter, having fallen from the trees above. Most species rot rapidly in such situations, while those other species found terrestrially are either in open, scrub-like habitats ( H. caminiferum [17] and H. dentrecastense [41]) or are only terrestrial above the tree-line ( H. archboldianum [36] and H. pauper [24]).