Hydnophytum longiflorum A.Gray

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 : 81-82

52. Hydnophytum longiflorum A.Gray — Fig. 55

Hydnophytum longiflorum A.Gray (1858) 42; Seem. (1866) 138 p.p.; Drake (1890) 199; Hook.f. (1894) t. 7343; Parham (1964) 193 p.p.; (1972) 272 p.p.; A.C.Sm. (1988) 244, f. 90: c–f. — Type: US Expl. Exp. 62267 (US), Fiji, Ovalau, 1840.

Squamellaria wilkinsonii (Horne ex Baker) Chomicki in Chomicki & S.S. Renner (2016) 20. — Hydnophytum wilkinsonii Horne ex Baker (1883) 365, as H. wilkinsoni ; Horne (1881) 263, nom. nud.; Becc. (1884) 125; (1885) 170, t. 44: 1–12; Drake (1890) 200; Parham (1964) 193; (1972) 272;A.C.Sm. (1988) 245. — Type: Horne 1077 (erroneously published as 1078 in Beccari 1885) (lecto K barcode K000761990; iso GH, K barcode K000761991), Fiji, Vanua Levu, Mbua, Sept. 1878, syn. nov.

Hydnophytum horneanum Becc.(1884) 125;(1885) 168,t. 43:15–25 (legend on plate as ‘ H. horneianum ’); Parham (1964) 193; (1972) 272. — Hydnophytum borneanum Becc. Sphalm. Govaerts et al. (2015) . — Type: Horne 282 (K), Fiji.

Squamellaria tenuiflora (Becc.) Chomicki in Chomicki & S.S.Renner (2016) 20. — Hydnophytum tenuiflorum Becc.(1884) 125; (1885) 169,t. 43:1–14; Parham (1964) 193; (1972) 272. — Type: Graeffe 1573 (lectotype selected by Smith (1988) K), Fiji, Ovalau.

non Hydnophytum longiflorum auct. non A.Gray (1858); A.Gray (1862a) 318; (1862b) 36 p.p.; Seeman (1862) 438; (1866) 138 p.p.; Drake (1890) 99; Becc. (1885) 172, t. 45: 1–7 p.p.; Parham (1964) 193; (1972) 272. quae = H. grandiflorum .

Tuber clasping, flattened to rounded, irregular, to 30 by 27 cm. Surface brown, usually sparsely bearded with flexible, slightly recurved spines. Entrance holes scattered, of two types, conical to 4 mm, or funnel-like and irregular. Stems several to numerous, branching freely, erect to upcurving, to 40 by 0.8 cm. Internodes to 7 cm when sterile, 0.5–3 cm when fertile. Leaves erect to spreading. Lamina elliptic, 3 by 1 to 11.4 by 4 cm; apex rounded to acute; base tapered, attenuate; midrib prominent below; veins 4–6; leathery. Petiole 0–1 cm; stipules rounded, to 0.2 cm, with a short, recurved central process to 0.1 cm, which is contiguous with stem ridge; caducous. Inflorescence terminal and axillary, solitary, shortly pedunculate, to 1.5 cm. Bracts to 1 mm papery, more or less persistent. Flowers [6] heterogamous. Calyx 4-cuspidate or entire, to 1 mm. Corolla tube 10–18 mm; lobes elliptic to rounded, 2.5–4 mm; uncus <1 mm; entirely glabrous within. Anthers exserted at mouth of corolla tube. In female-sterile flowers, anthers 1.5–2 mm, containing 4-colpate pollen, 74–94 μm, wall 7.5 μm thick, reticulation coarse, brochi 6–12 μm across, with fine spines within reticulations. In male-sterile flowers anthers 0.5–1 mm, containing no pollen, stigma exserted, capitate, broadly 4-lobed, to 1.5 mm across. Disc prominent to 1 mm above level of calyx, persistent in fruit. Fruit turbinate, flattened, to 7 by 4 mm; with prominent disc at apex; siccate; green and pink or red in colour when ripe. Pyrenes wedge-shaped, to 5 by 2 mm, blunt and rounded at apex, truncate and flattened at base.

Ecology & Habitat — Mangroves to montane forest, sea level to 900 m. Usually ant-inhabited, with about 50 % of individual tubers occupied by the ant species Philidris nagasau Mann.

Distribution — Fiji Islands (Viti Levu, Ovalau and Vanua Levu).

Conservation status — Vulnerable (VU) under criteria B1ab (iii)+2ab(iii). This species is found on three islands, with herbarium specimens indicating eight locations (subpopulations) and an AOO of 76 km 2 (using a cell width of 2 km). Other information: georeferenced collections 21, EOO on Viti Levu 1 900 km 2.

Notes — Squamellaria wilkinsonii , as interpreted by Beccari (1884), with a cuspidate fruit, is regarded, by us, as an artefact of drying, and here synonymised with H. longiflorum . Smith (1988) has already reduced H. horneanum and S. tenuiflora , which were based on inconsequential differences in calyx shape and corolla length, respectively.

More regularly ant-inhabited than H. grandiflorum , this species is distinguished by having a tuber that is more usually (but not invariably) covered by numerous slender roots, a shorter corolla, that is quite glabrous within, and a flattened, turbinate fruit. Two of the taxa we recognise as synonymous with H. longiflorum – S. tenuiflora and S. wilkinsonii – have been transferred to Squamellaria by Chomicki & Renner (2016). They indicated that they considered three taxa as possible synonyms of S. tenuiflora (Becc.) Chomicki , namely H. longiflorum , H. grandiflorum and H. horneanum . They did not make the specific transfer pending DNA sequences from the type specimens. However, the dates of publication for these taxa – H. longiflorum (1858), H. tenuiflorum (1884), H. grandiflorum (1884) and H. horneanum (1884) – leaves no doubt that the name H. longiflorum has priority and is therefore used here.

The misspelling of the name H. borneanum , instead of H. horneanum , by Govaerts in the Kew Checklist for Rubiaceae (2015) has entered IPNI (2015) and The Plant List (2015), as pointed out by Low et al. (2016)

Figures

Fig. 55 Hydnophytum longiflorum A.Gray. a. Shoot; b. male-sterile flower; c. female-sterile flower; d. fruit broad axis; e. fruit narrow axis; f. pyrene abaxial face; g. pyrene lateral view (a: Jebb 446; b–g: Jebb 441). — Scale bars: a = 7.5 cm; b, c = 5 mm; d–g = 10 mm. — Drawn by Rosemary Wise.