Eusideroxylon zwageri Teijsm. & Binn., Natuurk. Tijdschr. Ned. Ind. 25 (1863)
Named after J. Zwager [1824-?], a Dutch governor in Borneo.

Description
Mid-canopy tree up to 36 m tall and 95 cm dbh. Stipules absent. Leaves alternate, simple, penni-veined, glabrous to slightly hairy below. Flowers ca. 2.6 mm diameter, white-yellow, placed in panicles. Fruits ca. 84 mm long, grey-green, stony drupes.

Ecology
In undisturbed mixed dipterocarp forests up to 600 m altitude. Usually on hillsides with sandy soils, but also on alluvial flats. Capable of regeneration via sprouts when cut. Tendency to dominate forest stands. In secondary forests usually present as a pre-disturbance remnant tree.

Uses
The wood is very strong and durable, used for heavy construction.

Distribution
Peninsular Malaysia, Sumatra, Java, Borneo (throughout the island), Philippines, Moluccas.

Local names in Borneo
Belian, Belian timun, Betian, Talion bening, Tebelian geriting, Telianoii, Teluyan, Ulin, Ulin bening, Ulion.