Dissochaeta sarawakensis (M.P.Nayar) J.F.Maxwell, Gard. Bull. Singapore 33: 321. 1980.

Kartonegoro, Abdulrokhman, Veldkamp, Jan Frits, Hovenkamp, Peter & Welzen, Peter van, 2018, A revision of Dissochaeta (Melastomataceae, Dissochaeteae), PhytoKeys 107, pp. 1-178 : 1

49. Dissochaeta sarawakensis (M.P.Nayar) J.F.Maxwell, Gard. Bull. Singapore 33: 321. 1980. Map 26

Neodissochaeta sarawakensis M.P.Nayar, Bull. Bot. Surv. India 11: 195. 1969.

Type.

Malaysia. Sarawak: Pengkulu Ampat, G.D. Haviland 69 (holotype: K [K000859625]!).

Description.

Climbing up to 9 m in height; branchlets terete, 3-4 mm in diameter, covered with thin, 1-2 mm long bristle hairs; nodes swollen, with distinct crest-like interpetiolar ridges, margin bristly, up to 4 mm wide; internodes 2-5 cm long. Leaves: petioles terete, 4-7 mm long, sparsely stellate-puberulous and with scattered bristles at dorsal groove; blades ovate to elliptic, 5-6 × 2.3-3.8 cm, subcoriaceous, base rounded to subcordate, margin entire, apex acuminate, tip ca. 0.5 cm long; nervation with 1 pair of lateral nerves and 1 pair of intramarginal nerves; surfaces glabrous, sometimes abaxially with pair of glandular patches at base. Inflorescences terminal, up to 10 cm long, many-flowered; main axis stellate-furfuraceous; primary axes up to 4 cm long with 2 or 3 nodes, secondary axes 1-2 cm long with 1 or 2 nodes, tertiary axes up to 0.8 cm long with 1 node; bracts linear, 2-3 mm long, glabrous; bracteoles subulate, ca. 1 mm long, stellate-furfuraceous; pedicels furfuraceous, 3-4 mm long in central flowers, 1-2 mm long in lateral flowers. Hypanthium campanulate, 2-3 × ca. 2 mm, glabrous; calyx lobes truncate, ca. 0.5 mm long, with 4 small minute points; petal buds conical, 2-3 mm long, apex narrowly acuminate, glabrous; mature petals ovate, ca. 5 × 3.5 mm, glabrous, reflexed, base clawed, apex acute, white or pale pink. Stamens 8, equal, filaments curved sideways; alternipetalous stamens with 3-4 mm long filaments, anthers oblong, curved, sickle-shaped, thecae 3-4 mm long, yellow, pedoconnective short, ca. 0.5 mm long, basal crest ligular, bi- or trifid, ca. 2 mm long, lateral appendages paired, filiform, 4-5 mm long; oppositipetalous stamens with 3-4 mm long filaments, anthers S-shaped, thecae 3-3.5 mm long, yellow, basal crest ligular, ca. 1.5 mm long, lateral appendages paired, filiform, ca. 2 mm long. Ovary ⅔ of hypanthium in length, apex glabrous; style glabrous, ca. 9 mm long, reddish; stigma minute; extra-ovarial chambers absent or not developed. Fruits globose, 2-3 × ca. 2 mm, glabrous; calyx lobe remnants persistent. Seeds ca. 0.5 mm long.

Distribution.

Borneo (Brunei and Sarawak).

Ecology and habitat.

Heath forest or mixed dipterocarp forest at 240-1000 m elevation.

Vernacular names.

akar kemunting (Iban); akar kitum (Kenyah).

Note.

Vegetatively similar to D. stipularis in its distinct wide, crest-like interpetiolar ridges and glabrous leaf blades. The difference is that D. sarawakensis has fertile alternipetalous stamens, which are equal to the oppositipetalous ones, while in D. stipularis the alternipetalous stamens are staminodes, reduced and smaller than the oppositipetalous ones.

Specimens examined.

MALAYSIA. Sarawak: Pengkulu Ampat, G.D. Haviland 69 (K); Baram, Gunung Mulu, 365 m, 4 Jul 1961, J.A.R. Anderson & H. Keng K7 (BO, K, L); Ibid., Ulu Tinjar, Dulit Range, 300 m, 9 Aug 1974, P.K. Chai S.34713 (K, L); Balingian, Bawan, Begrih, 10 m, 20 Oct 1963, P.K. Chai S.19481 (K); Bintulu, Segan FR., 244 m, 18 Aug 1968, Ilias Paie S.27040 (BO, K, L); Kuching, Mount Matang, 396 m, 27 Mar 1929, J. Clemens & M.S. Clemens 20929 (BO, K); Kapit, Batang Rejang, Batu Laga, 1000 m, 12 Sep 1984, Abang Mochtar S.48265 (K, L); Sri Aman, Gunong Silantek, 530 m, 27 Aug 1980, Ilias Paie S.42599 (K, L). BRUNEI. Temburong: Amo, Bukit Tudal, 840-1160 m, 6 Oct 1994, P.C. Bygrave et al. 29 (K, L).

Figures

Map 26. Distribution of D. sarawakensis (■), D. schumannii (▲) and D. spectabilis (●).