Macaranga costulata Pax & K.Hoffm., Pflanzenr. IV, 147, VII: 338 (1914)
Name meaning 'clear veins', probably refering to the leaf venation.
Small trees up to ca. 25 m tall and 25 cm dbh, reproductive from 2 m tall and 2 cm dbh. Twigs solid, usually hairy. Stipules triangular
to ovate, usually semi-persistent, 2-12 mm long by 1.5-3 mm wide. Petioles glabrous to hairy, up to 10 cm long. Leaves alternate, ovate,
peltate or not, 7-20.5 cm long by 2.5-12 cm wide, length/width-ratio 1.3-3.4; secondary veins 9-17, usually not ending in the margin;
leaf base not to slightly cordate, peltate margin length (when present) 0.1-0.6 mm; leaf upper surface glabrous, with 2-4 basal nectary
glands directly next to petiole insertion; leaf lower surface glabrous to hairy, densely gland dotted. Staminate inflorescences branched;
flowers clustered per bracteole; bracteoles with entire margin. Pistillate inflorescences branched; fruits 2-3 mm wide, 2-locular,
completely covered with yellow glands.
Trees, usually only 5(-25) m. Twigs solid, slender, to 4 mm diam., terete, weakly furfurescent.
Stipules broadly elliptic, to 10 by 2mm, papery, pubescent, erect, soon caducous. Leaves: petioles
c. 6 cm, slender, terete, finely ridged, (almost) glabrous, not kneed; blades ovate-oblong to
trullate, 10(-15) by 4-7(-12) cm, papery, base broadly truncate occasionally 1-3 mm peltate, rarely
cordulate, 2 large conspicuous glands at petiole insertion, margin entire sometimes very weakly
crenate rarely shallowly dentate, apex acute to abruptly acuminate, usually drying pale greenish
khaki, below sparsely pubescent on main nerves. Staminate inflorescences crowded, broad fairly dense
delicate panicles to 8 by 5 cm, 3 axis orders, finely furfuraceous to almost glabrous; main branches
divaricate; peduncle short, 3-10 mm; main axis slender, under 1 mm diam., roundish, coarsely
striate; lower branches alternate, axillary branches very rare; bracts not seen; branches
thread-like, tertiary branches arising from flower clusters on secondaries; flower clusters evenly
spaced, distant, 5-10 mm apart; bracteoles linear, 3-4 mm, distorted by 1-3 patellar glands, or
pointed, occasionally with a few marginal teeth, glabrous, base spathaceous, enclosing cluster,
spreading, conspicuous, persistent. Staminate flowers c. 15 per cluster, developing sequentially,
0.5 mm diam., sessile; sepals 3, glabrous; stamens 3, anthers 4-locular. Pistillate inflorescences
crowded, delicate, diffuse narrow racemes or spikes, to 10 cm long, as staminate. Fruits in groups
of 1-3, depressed globose, slightly flattened, weakly bilobed, 2 by 3 mm, finely golden granular
glandular; pedicel thread-like, 1 cm; calyx tiny, persistent; styles 2, short, recurved, apical.
Seeds with sarcotesta, shallowly coarsely rugose. [from Flora Malesiana]
Collected up to ca. 1800 m altitude. In primary and secondary forests. On clay, dark brown, limestone
and sandstone soils.
Endemic to Borneo.