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.