Description from Flora of China
Herbs, perennial or rarely annual, aquatic or of marshes, sometimes rhizomatous. Leaves basal, linear, lanceolate, elliptic to ovate or orbicular, or sagittate, with elongated sheathing petioles; principal veins parallel with margins and converging toward apex and connected by transverse veins. Flowers often whorled at nodes of scape forming racemes, panicles, or umbels, pedicellate, actinomorphic, bisexual, unisexual, or polygamous, usually bracteate. Sepals 3, persistent, green. Petals 3, deciduous, usually white, sometimes yellowish. Stamens 3 to numerous, whorled, with elongated filaments; anthers 2-celled, extrorse, opening by longitudinal slits. Carpels 3 to numerous, whorled or spirally arranged, free; ovules 1 to several; style persistent. Fruit a cluster or whorl of laterally compressed achenes, drupelets, or occasionally follicles. Seeds curved, with a horseshoe-shaped embryo; endosperm absent.
Chen Yaodong. 1992. Alismataceae. In: Sun Xiangzhong, ed., Fl. Reipubl. Popularis Sin. 8: 127-145; Zhou Lingyun. 1992. Butomopsis and Limnocharis. In: Sun Xiangzhong, ed., Fl. Reipubl. Popularis Sin. 8: 147-151.
About 13 genera and ca. 100 species: cosmopolitan, especially abundant in temperate and tropical regions of the N Hemisphere; six genera (one introduced) and 18 species (three endemic, one introduced) in China.
(Authors: Wang Qingfeng (王青锋); Robert R. Haynes, C. Barre Hellquist)