Lasianthus sumatraensis H.Zhu, 2012

121. Lasianthus sumatraensis H.Zhu View in CoL , sp. nov. — Fig. 37 View Fig

Similis L. malaiense H.Zhu , sed foliis basi acutis praeter costae et nervis subtus glabris, cyma ramosa, floribus pedicellatis, lobis calycis linearis 5 mm longis differt.A L. scalariformis King & Gamble ramulis dense brunneo-tomentosis,costis et nervis subtus brunneo-tomentosis,foliis ovato-ellipticis et lobis calycis linearibus tomentosis differt. — Typus: De Wilde et al. 13225 (holo L), North Sumatra, Kutatjane, 2500 m alt., in montane mossy forest, 23 June 1972.

Shrub, up to 4 m high; branchlets terete, densely brown tomentose. Leaves: blades ovate-elliptic, 7–11 by 2.5–4.5 cm, coria- ceous, glabrous except venation beneath, apex acute to acuminate, margin ciliate, base acute to subrounded,midrib depressed above, prominent beneath, brown tomentose beneath, nerves flat above, prominent beneath, 6 –7 pairs, ascending at an angle of 50–60°, curved to the margin, tomentose beneath, nervules prominent on both surfaces, conspicuous, parallel, pubescent to glabrescent beneath; petioles 1–1.5 cm long, brown tomentose. Stipules lanceolate, 3–4 mm long, tomentose. Inflorescences cymose, brown tomentose; the main peduncles 5 –10 mm long, peduncles branches (if present) c. 5 mm long; bracts linear, 2 in each node, 5 mm long, brown hirsute; bracteoles 2, linear, 3 – 5 mm long, brown hirsute. Flowers pedicellate; pedicels 1–3 mm long, brown tomentose; calyx campanulate, densely brown tomentose, lobes 5, linear, 5– 6 mm long, densely tomentose external surface. Drupes subglobose, 5-ridged, crowned by persistent linear, 5 mm long, calyx lobes; pyrenes 5, smooth on the abaxial face, suborbicular in transverse section.

Distribution — Sumatra (northern part).

Habitat & Ecology — In montane rainforest to mossy forest between 1600–2600 m altitude. Flowering and fruiting between May and August.

Additional specimens examined. North Sumatra, Atjeh, 2400–2600 m alt., W.J.O. de Wilde et al. 16785 (K, L); Atjeh, 1600–1800 m alt., K. Iwatsuki et al. S.958; Atjeh, Van Steenis 9545 (L).

Note — This species is quite similar to L. malaiense . It differs from the latter by having leaves with acute base, glabrous except venation beneath; cymes branched; flowers pedicellate; calyx lobes linear, 5 mm long. While L. malaiense has leaves with rounded base, villose beneath; cyme capitate; peduncles 2 – 3 cm long; flowers sessile; calyx lobes lanceolate, 2.5 mm long. It differs from L. scalariformis by having dense brown tomentose hairs on branchlets, leaf midrib and nerves beneath; ovate-elliptic leaves; calyx lobes linear, densely tomentose. While L. scalariformis has leaves subglabrous, elliptic-lanceolate; calyx lobes oblong-lanceolate, sparsely hirsute.