Hydnophytum caminiferum Wistuba, U.Zimm., Gronem. & Marwinski

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 : 51

17. Hydnophytum caminiferum Wistuba, U.Zimm., Gronem. & Marwinski — Fig. 20

Hydnophytum caminiferum Wistuba,U.Zimm., Gronem.& Marwinski (2014) 45. — Type: Wistuba 2014­001 (M not seen) from cultivated material (ex New Guinea,West Papua Province,Manokwari,Anggi Lakes),8 Mar.2014.

Hydnophytum cecilia Jebb & C.R.Huxley, Naturalis Biodiversity Center (NL) , http://bioportal.naturalis.nl/ (accessed 17 Oct. 2017); JSTOR, http:// plants.jstor.org/stable/10.5555/al.ap.specimen.k000761975 (accessed 17 Oct. 2017); GBIF Backbone Taxonomy, Checklist Dataset https://doi. org/10.15468/39omei (accessed via GBIF.org on 17 Oct. 2017, https:// www.gbif.org/species/8943207), nom nud.

Terrestrial shrub. Tuber upright, to 60 cm high, an aggregation of amphora-shaped tubers with upwardly opening cavities each with 1 or 2 entrances. Entrance holes 1–2 cm across; lipped and ± oriented upwards, standing prominently from surrounding tuber surface. Cavities all smooth-walled, new tuber tissue arising as swollen stems which eventually become hollow, opening at their apex; the majority of cavities comprise U-shaped chambers opening by two openings, one opening higher than the other. Stems mostly confined to apex of tuber, but also arising laterally from tuber and on side tubers; solitary to numerous, little branched, straight to zigzagged; to 40 by 0.2–0.4 cm; internodes 0.5–1.5 cm in length. Leaves sessile, clustered at apices, falling by the 5th or 6th node; held upright close to stem. Lamina cordate, 1.3 by 1.1 to 1.6 by 1.3 cm; apex blunt to acute, base cordate; thick, fleshy, margin recurved; white below; midrib prominent below, becoming inconspicuous in upper 1/3, veins c. 5 indistinct. Stipules to 0.15 cm, triangular, persistent. Inflorescences paired swollen tubercles, to 0.5 cm across, a prominent cushion of papery and brown bract hairs to 3 mm in length. Flowers [1]?heterostylous. Calyx to 2 mm; margin with a fringe of septate hairs to 2 mm. Corolla white, 14 mm long; tube 10 mm; lobes 4 mm; with four patches of hairs at the mouth of the tube. Anthers dark purplish brown, exserted, 1.5 mm long; filaments 2.5 mm. Pollen 56 μm, 3-colpate, coarse vermiculate reticulation. Stigma 2-lobed, about 1/3rd the way down the corolla tube; style 5–7 mm. Fruit red, to 5 mm. Pyrenes obovoid, 4 by 2 mm; apex rounded; base attenuate.

Ecology & Habitat — Terrestrial in open scrub and woodland on quartzite soils surrounding the Anggi Lakes in the Arfak Mountains, between 2 000–2 600 m. The tuber is once reported with ants, but usually the cavities contain rainwater and various arthropods other than ants.

Distribution — Indonesia (West Papua Province).

Conservation status — Critically Endangered (CR) under criteria B1ab(i,ii,iii,v)+2ab(i,ii,iii,v). This taxon is terrestrial on the ridge tops around the Anggi lakes, this habitat has a total area of under 10 km 2 and is prone to regular fires. It is inferred that the EOO and AOO of this taxon will decline as well as being degraded. A species of Myrmephytum , M. arfakianum (Becc.) C.R.Huxley & Jebb , is also found as a terrestrial plant on these ridges, but it is also found epiphytically in the surrounding forest, while H. caminiferum is not.

Additional specimens examined. Jebb 890 (BO, K, L, LAE ), S1°23' E133°55',ridge between Anggi Gigi and Anggi Gita lakes,Dec.1990; Sleumer & Vink in BW 14216 (L) S1°25'E133°51',Anggi Gigi lakes, Mt Sensenemes, 18 Jan. 1962; Kanehira & Hatusima 14062 (FU), Mt Koebre, Anggi lakes.

Notes — The tuber of this species is remarkable in form, and unique within the genus. The flask-shaped tuber comprises a number of unconnected, U-shaped cavities, with upward-facing entrance holes 1–2 cm diam. Each cavity has 2 openings, at different heights, rarely, in young plants they may have only a single opening. Cavities are added both apically, apparently through swelling of the stems, and basally, along the lower perimeter of the tuber. The cavities contain trapped rainwater and detritus, but as pointed out by Wistuba et al. (2014) the positioning and structure of the entrance holes does not appear to be efficient at capturing rainfall.

Three other species of Hydnophytum have small cordate leaves: – H. cordifolium [40] has larger leaves and pedunculate inflorescences; H. orichalcum [46] has linear-cordate leaves; H. ovatum [4] has swollen nodes with a socket-like inflorescence. We had intended to publish this species with the name H. cecilia and the proposed type material (Jebb 890) was distributed under that name.

Figures

Fig. 20 Hydnophytum caminiferum Wistuba, U.Zimm., Gronem.& Marwin- ski. a. Whole plant with some shoots; b. whole young plant; c. half flower (Jebb 890 (BO, K, L, LAE) West Papua Province, Vogelkop, ridge between Anggi Gigi and Anggi Gita lakes, Dec. 1990). — Scale bar: a, b = 10 cm; c = 10 mm. — Drawn by Rosemary Wise.