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Itoa comprises two species, one in southern China and Indochina (I. orientalis), which is in cultivation, and another in eastern Indonesia (I. stapfii (Koord.) Sleumer). The two species are very similar, and if it were not for their divergent distributions they might easily be lumped together. They are evergreen trees with large, simple, spirally arranged leaves; the leaves have a sturdy petiole, crenate margins and no stipules. Both species are dioecious, the staminate flowers held in erect, terminal panicles, the pistillate flowers solitary and axillary. The flowers have a leathery, valvate calyx, with three (to four) lobes, and no petals; the staminate flowers have numerous stamens, the anthers minute. The fruit is a large, egg-shaped capsule, which eventually divides (partially) into (five to) six to eight segments, releasing numerous winged seeds (Sleumer 1954).