Dissochaeta alstonii M.P.Nayar, Bull. Bot. Surv. India 11: 188. 1969.

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

2. Dissochaeta alstonii M.P.Nayar, Bull. Bot. Surv. India 11: 188. 1969. Map 2

Dissochaeta rostrata Korth. var. alstonii (M.P.Nayar) J.F.Maxwell, Gard. Bull. Singapore 33: 318. 1980.

Type.

Indonesia. North Sumatra: Tapanuli, between Sidikalang and Pongkolan, 1200 m elev., 27 Mar 1954, A.H.G. Alston 14813 (holotype: BM [BM000944479]!).

Description.

Branchlets terete, 3-4 mm in diameter, covered with stellate hairs and glandular bristles; nodes swollen, with an interpetiolar ridge; internodes 4-7 cm long. Leaves: petioles terete, 5-8 mm long, densely stellate-furfuraceous; blades ovate, 6-8.5 × 3-4 cm, subcoriaceous, base subcordate, margin entire, ciliate, apex acuminate, tip ca. 1 cm long; nervation prominent above, with 1 or 2 pairs of lateral nerves and 1 pair of intramarginal nerves; adaxially glabrous and with scattered bristle hairs on midrib, abaxially punctate, midrib with dense stellate hairs, brown furfuraceous and bristle hairs. Inflorescences terminal, many-flowered, 20-30 cm long; main axis angular, densely setose with glandular bristles and stellate-furfuraceous hairs; primary axes up to 28 cm long with 6-8 nodes, secondary axes 1.5-4 cm long with 1-3 nodes, tertiary axes up to 1 cm long with 1 node; bracts linear, 3-6 mm long, densely setose with glandular bristles; bracteoles linear, 3-4 mm long, densely setose with glandular bristles; pedicels densely setose with glandular bristles, 2-3 mm long in central flowers, 1-2 mm long in lateral flowers. Hypanthium campanulate, tubular, 4.5-5.5 × 2-3 mm, densely setose and covered with glandular bristles and stellate-furfuraceous hairs; calyx lobes triangular, 2.5-3 mm long, densely setose; petal buds conical, 3-4 mm long; mature petals obovate to ovate-oblong, ca. 4.5 × 2.5 mm, base clawed, apex acuminate, glabrous but glandulose-setose at margin, pink. Stamens 8, unequal, glabrous, filaments curved sideways; alternipetalous stamens with 4-4.5 mm long filaments, anthers rostrate, sickle-shaped, thecae 4.5-5 mm long, pedoconnective ca. 0.5 mm long, basal crest erose, up to 0.4 mm long, lateral appendages subulate, paired, ca. 2 mm long; oppositipetalous stamens with ca. 3.5 mm long filaments, anthers hook-shaped, thecae 3.5-4 mm long, basal crest minute, erose, ca. 0.2 mm long, lateral appendages minute, ca. 0.2 mm long. Ovary half as long as hypanthium, apex stellate-furfuraceous; style 9-11 mm long, glabrous, apex curved; stigma punctiform; extra-ovarial chambers 8, extending to near the base of ovary. Fruits subglobose, 4.5-5.5 × ca. 4 mm, covered with dense glandular bristles and stellate-furfuraceous hairs; calyx lobe remnants persistent, reflexed. Seeds ca. 0.5 mm long.

Distribution.

Sumatra.

Ecology and habitat.

Montane forest at ca. 1200 m elevation.

Note.

Dissochaeta alstonii is known only from the type from Northern Sumatra. The species resembles D. rostrata , by having a setose and bristly appearance on branchlets and hypanthium. It differs by having glandular bristles in most parts, like branches, leaves and hypanthium while, in D. rostrata , the bristles are simple, not glandular.

Figures

Map 2. Distribution of D. acmura (●), D. alstonii (■) and D. angiensis (▲).