Infl. a bractless spike, at first wrapped in sheaths of subtending lvs; peduncle unbranched and later elongating; fls 2, contiguous, borne laterally on opp. sides near tip of peduncle, one above the other. Fls small, greenish, bisexual. Per. 0. Stamens 2, almost sessile, each of 2 ± reniform, horizontally disposed, extrorsely dehiscing cells, separated by a broad connective. Carpels (2)–4–8–(16), superior, at first sessile and crowded together, later becoming stipitate and separated by elongation of "podogynes"; stigma appearing sessile, peltate or umbonate; ovule solitary, pend., campylotropous. Achenes or drupelets ± beaked, outer pericarp soon decaying, endocarp hard, splitting by separation of vertically oriented operculum. Aquatic herbs, us. submerged in brackish water; rhizome branched, rooting at nodes, giving off lfy stems. Lvs alt., sessile, simple, filiform-linear, 1-nerved, with long, open, stipular sheath. One genus, widespread in temperate and subtropical zones, us. near sea shore, rarely inland.