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Shrub to 2.5m, usually epiphytic, young stems at first finely scaly, quickly glabrescent. Leaves 8-16 x 4-6.5cm, elliptic or broadly elliptic occasionally lanceolate, the apex acute, often acuminate, the margin entire, slightly revolute, the base broadly to narrowly tapering, sometimes slightly asymmetric; the upper surface with a strongly raised midrib in the basal half, the laterals 5-10 pairs only slightly raised or smooth, very finely scaly at first, quickly glabrescent; the lower surface with the midrib raised throughout its length, the laterals rather obscure, scales very small, brown, rounded to lobed. Umbels 4-12 flowered, erect to half-hanging; calyx disc-shaped sometimes with low lobes, almost glabrous; corolla yellow variably and sometimes heavily flushed orange, funnel-shaped, 3-3.5 x 3-3.5cm, glabrous outside; stamens 10, somewhat irregularly arranged in the mouth of the flower; ovary glabrous, or with a few scales, the style completely glabrous.
Distribution West Malaysia (from Perak to Selangor and in the Taiping Hills).
RHS Hardiness H1b.
Distinguished from most forms of the very similar R. brookeanum by its almost glabrous ovary and glabrous filaments.