Flora of New Zealand Series

Annual or perennial herbs; stems erect, creeping, procumbent or decumbent, sometimes floating. Lvs opposite, entire, sessile or petiolate. Infls sessile or pedunculate, capitate or spicate, usually axillary; fls usually ⚥, sometimes ♀, each with a scarious bract and 2 scarious bracteoles. Tepals 5-merous, often dorsally compressed, equal or unequal, free, glabrous or hairy. Stamens 2-5; filaments connate in a short tube at the base; staminodes sometimes present; anthers small, 1-celled. Ovary compressed or terete; ovule 1, pendulous on long funicle. Style short; stigma capitate. Fr. an utricle, indehiscent, often compressed, with persistent perianth, falling with or without bracteoles. Seed vertical.

150-200 spp., mainly tropical and subtropical America, a few spp. in Old World tropics. Naturalised spp. 3.