Tree 4-15 m. Leaves membranous, (elliptic-)oblong, 12-28 by 4-12 cm, base attenuate, apex acute-acuminate; Inflorescences with sparse hairs 0.1 mm or less; Fruits 2-6 per infructescence, glabrous, ovoid-ellipsoid, 2.2-2.5 by 1.6-1.8 cm, with or without a few small lenticel-like tubercles;
Asia-Tropical, northern and central Sumatra present
Malesia: northern and Central Sumatra.
1 Related to H. glabra, with similar fruits and flowers. Horsfieldia macrothyrsa has markedly larger male flowers, and about twice as many anthers. It has a different distributional area; H. glabra is not found in C and N Sumatra. 2 The specimens of H. macrothyrsa rather differ from each other in various aspects. Plants from Mt Sago (= Mt Malintang), C Sumatra, are less robust in general habit, the leaves and inflorescences are smaller, the male buds 3-3.5 mm diameter. Specimens from Sibolangit Botanic Garden jungle are stout, with large leaves (to 28 cm long), large j male buds (4.3 by 4 mm), and deviate furthermore by the slightly raised nerves on the upper leaf surface.