Onagraceae A. L. Jussieu
Circaea by BOUFFORD, DAVID E., Epilobium by LIEVENS, ALAN W. and HOCH, PETER C., Ludwigia by RAVEN, PETER H. and PENG, CHING-I, Oenothera by HOCH, PETER C. and WAGNER, WARREN L.
Annual, biennial or perennial herbs, sometimes woody. Leaves basal or cauline, alternate or opposite, simple, entire or toothed (rarely lobed); stipules minute or absent. Flowers actinomorphic or zygomorphic, in leaf axils or in inflorescences, generally bisexual (all in Taiwan), 2-7-merous; floral tube present or absent; stamens as many as or twice as many as the sepals; anthers versatile; pollen shed singly or in tetrads, connected by viscin threads; ovary inferior; style single; stigma 4-lobed, clavate or globose. Fruit a capsule, berry, or nut, loculicidal or indehiscent. Seeds anatropous, lacking endosperm, smooth or with tubercles or scales, some with a coma or wings.
Fifteen genera and about 650 species, worldwide but with most genera present in western North America. All four genera that occur as native plants in the Old World have representatives in Taiwan, and a total of 22 species (plus one hybrid) of Onagraceae occur in Taiwan.