Description from Flora of China
Trees, dioecious (or ?monoecious), evergreen. Leaves usually alternate, sometimes subopposite; stipules early caducous; petiole long, without glands at apex nor along length; leaf blade pinnate-veined, lateral veins closely set, mostly 1(-2) cm apart, margin glandular-serrate or glandular-crenate, sometimes minutely so. Flowers unisexual, hypogynous; staminate flowers in erect, terminal panicles; pistillate flowers 1 to few in short terminal or axillary racemes; bracts present; bracteoles 1 pair per pedicel, usually caducous. Pedicels not obviously articulate in dried material. Sepals appearing 3- or 4-merous in bud, in fact to 5-merous at anthesis, nearly free, valvate, ovate, with base appearing ± cordate when sepal erect, texture rather thick, margins slightly conduplicate. Petals absent. Disk glands absent. Staminate flowers: stamens many; filaments free, filiform; anthers ellipsoid to oblong, basifixed, connective usually curved, bringing both locules to face in same direction (toward periphery of flower); abortive ovary present. Pistillate flowers: ovary superior, 1-loculed; placentas 6-8, rarely 5, filiform, finally woody, persistent; ovules numerous; styles 6-8, very short, connate, forming a short longitudinally ribbed column; stigmatic branches (4-)6-8, spreading or strongly reflexed against ovary, irregularly palmately lobed; staminodes many, extragynoecial, like stamens but very much reduced. Capsule ovoid or ellipsoid, large, woody, tomentose, outer layer probably finally dehiscent; valves (5 or)6-8, fusiform, splitting from apex and base and remaining attached by woody persistent placental strips; styles caducous. Seeds many, arranged vertically in capsule, winged; wing broad, flat, thin, triangular, squarish or rectangular, completely surrounding seed; seed proper small.
Itoa has been reported as dioecious (e.g., Sleumer, Flora Males., ser. 1, 5(1): 12. 1954) but might also be monoecious. Hoogland 5079, a specimen of I. stapfii (Koorders) Sleumer from New Guinea, has a short raceme bearing a pistillate flower with young fruit developing, and a staminate flower with pollen-bearing anthers. In dried specimens of Itoa seen for the present account, the majority of flowers were in bud; those dissected contained stamenlike structures that may be stamens or staminodes.
Two species: Asia; one species in China.