Trees, shrubs or climbers, rarely herbs. Leaves simple or compound, alternate, exstipulate or stipules caducous; leaflets opposite or alternate, entire to lobed. Flowers small, usually paniculate, sometimes in cymes or fascicles, unisexual, actinomorphic or obliquely zygomorphic. Sepals 3-5, often unequal. Petals 3-5, sometimes absent, equal or unequal, often with basal scales. Disc unilateral or annular, sometimes absent in the male flower. Stamens 5-10; staminodes present. Ovary superior, centric or excentric, 1-6-locular; placentation axile, rarely parietal; ovules 1-2 in each locule. Fruit a nut, a berry or a capsule, sometimes winged. Seeds globose to oblong or compressed, often arillate.
A tropical and sub-tropical family of 150 genera and about 2000 species.
Acknowledgements: We are grateful to the United States Department of Agriculture for financing this research under P.L. 480. Thanks are also due to Miss J. Lamond and Messrs B. L. Burtt and I.C. Hedge of the Royal Botanic Garden, Edinburgh, for their helpful suggestions.