Trees, often growing to enormous size; buttresses absent; white latex in all plant parts. Branchlets usually strongly longitudinally ribbed when young, occasionally weakly so. Leaves in whorls; petioles relatively long with noticeable intrapetiolar stipules; blade often weakly crenulate at margin; glabrous. Inflorescence of umbelliform or paniculate cymes; lax or somewhat congested in upper parts; flowers 5-merous. Sepals with colleters inside; connate at base; lobes often of different sizes. Corolla lobes sinistrorse; mature corolla platter-shaped; lobes oblong to narrowly ovate, more or less symmetrical, auriculate at the base on both sides; glabrous outside and inside. Stamens free from the style head; completely included in the corolla tube; filaments short and narrow; anthers narrowly ovate, base cordate, apex apiculate, sterile at apex, dehiscing laterally. Disk annular; inconspicuous; adnate to the ovary. Gynoecium 2-carpellate, apocarpous but apically united into a common style and carpels closely associated and appearing syncarpous, pubescent; many ovules per carpel; style and style head short. Fruit of paired, divergent follicles, these heavy and woody, dehiscing at maturity. Seeds elliptic, flattened; with a broadly membranous wing.
UsesBoth species were previously tapped for making rubber and for the manufacture of chewing gum but this industry has greatly declined. Both also have a soft and easily worked timber but which is not durable. The wood is used for smaller items like pencils, picture frames, carving, toys, furniture parts, packing cases etc.
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