Dipterocarpus C.F.Gaertn.

Medium-sized to large trees with thick, rounded, usually small and concave, sometimes tall and straight buttresses. Crown usually relatively narrow, even or irregular (not cauliflower-shaped), dome-shaped, frequently rather flat, open, with a few large strongly ascending twisted branches. Bark surface pale or dark grey to orange-brown, sometimes pink-brown; appearing smooth, shallowly patchily flaked; or appearing square-section fissured, shaggy, with persistent oblong flakes; +-prominently densely warty lenticellate. Twigs variable, stout or slender, terete or compressed, glabrous or tomentose; with distinct, usually swollen and pale, amplexicaul stipule scars. Stipules large, hastate to lorate, obtuse, +-succulent, caducous, characteristically carpeting the forest floor in the growing season. Leaves coriaceous, rarely thin, margin usually sinuate towards the apex; nerves prominent beneath, straight, curved only towards the margin, with traces of the plicate vernation remaining persistently between them, giving the lamina a corrugated appearance (cf Parashorea); tertiary nerves scalariform; petiole distinctly geniculate, stout. Inflorescence racemose, short, stout, zig-zag, few-flowered, somewhat irregularly sparingly branched; bracts as stipules but smaller, fugaceous. Flowers large. Fig. 18. Buds ellipsoid. Calyx united round the fruit into a tube, but not fused to it; lobes valvate: 2 long, oblong to spatulate, ± distinctly 3-nerved, and 3 short, or all 5 short. Petals large, narrowly oblong, strongly contorted, loosely cohering at base on falling, cream with a prominent pink stripe down the centre. Stamens 15-40, persisting at first in a ring round the ovary after the petals fall; filaments of variable length, broad, compressed, connate at base, tapering apically, latrorse, with 4 pollen sacs, the inner 2 somewhat shorter than the outer 2; appendage to connective short, stout to long filiform, slender, glabrous. Ovary enclosed in the calyx tube, the apex ovoid to conical, shortly tomentose; stylopodium cylindrical to filiform, shortly tomentose, narrowing gradually or abruptly into the glabrous filiform style. Fruit large. Fig. 17. Calyx tube becoming ± distinctly constricted into a distal neck as the nut expands; lobes as in flower, but greatly expanded; nut ovoid, tomentose with a short acute apical style remnant. Germination hypogeal, the intricately folded subequal cotyledons remaining within the fruit and the plumule freeing itself by elongation of the cotyledonary petioles; seed sometimes albuminous at germination.

Evergreen forests and savanna woodland below 1400 m. Some species become semi-gregarious on river banks or alluvium (D. validus, D. elongatus), podsols (D. borneensis), ridges (several species) and semi-evergreen forest of seasonal climates (D. gracilis, D. costatus). Seedlings mostly require high light intensities for survival; the genus is least common in dense valley forests.

Uses. Light to medium timbers absorbing preservatives readily; used for railway sleepers and heavy construction. The oleoresin is tapped in the semi-evergreen forests of Indochina and Burma, and sometimes elsewhere, for varnishes and tallow, by cutting into the bole and wounding the tissues by burning.