Polygamous; sep, pet, and stamens 4 or 5, the latter imperfect or abortive in pistillate fls; ovary bilocular, with a short style and capitate, ±2-lobed stigma; ovules 2 per locule, superposed on axile placentas; fr a thin, flat, orbicular samara, the broad wing surrounding the indehiscent bilocular body; unarmed shrubs or small trees with alternate (opposite), petiolate, trifoliolate lvs and terminal cymes of small, greenish-white or yellowish-white fls. 3, temp. N. Amer.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.