Alstonia pneumatophora Backer ex Den Berger, Meded. Proefst. Thee 97 (1926)

Synonyms
Alstonia pneumatophora var. petiolata Monach.

Diagnostics
Tree with abundant white sap and pneumatophore roots. Leaves in whorls, usually with very short or without petiole and no ligule at base of petiole, lower surface whitish, secondary veins placed close together at perpendicular angle with midvein. Fruits very long and narrow, placed in pairs; splitting open to expose many small seeds with two tufts of hairs for wind dispersal.

Description
Large tree, 25-85 m tall, 30-100(-205) cm diameter; bole fluted at base and forming tall steep buttresses to 8 m high, to 3 m out; pneumatophore roots well-developed. Bark smooth or sparsely scaly, grey or yellowish grey; inner bark pale yellow or orange-brown, soft, granular, with copious white latex. Leaves in whorls of (3-)4-6, sessile or shortly petiolate, without a distinct intrapetiolar stipule at the base of petiole, subcoriaceous, grey-green above, brownish or dark red-brown below, glabrous on both sides; blade spatulate, sometimes obovate, 4.3-13 x 1.5-4.2 cm, base acute or tapering narrowly and evenly right down the petiole, rarely obtuse, apex rounded, sometimes retuse; midrib sunken above; lateral veins closely spaced and almost perpendicular to the midrib, 18-30 pairs; intercostal venation inconspicuous. Inflorescences 3-10 cm long, compound, forming two bunches of densely clustered flowers. Flowers fragrant; calyx pubescent outside, ciliate; corolla glabrous outside, white, 9-13 x 1-1.6 mm in mature bud, lobes overlapping to the left in bud, ovate, 3-4.3 x 2-3.2 mm, not ciliate, spreading in open flower; ovary ovoid, 0.8-1.2 x 0.7-0.9 mm, glabrous; disk obscure or absent. Fruits pubescent, 10-20 cm long, 1.5-2 mm diameter. Seeds oblong, 4-4.8 x 1-1.2 mm, ends rounded, glabrous on both sides; coma 8-12 mm long.

Ecology
In undistrurbed and disturbed forests up to 100 m altitude. Usually in swamps (freshwater- and peat-swamp) or alluvial sites.

Distribution
Peninsular Malaysia, Sumatra, Borneo and Celebes.

Local names
Borneo: Pulai lilin, Tambaelek.