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Annual or perennial, erect, ascending, trailing, creeping, floating or clambering herbs, often hairy; hairs dentate or smooth. Leaves opposite, entire. Flowers ☿ or by malformation ♀, in axillary or rarely terminal, sessile or peduncled heads or short spikes, solitary in axil of bract, subtended by 2 bracteoles; bracts and bracteoles scarious. Perianth often dorsally compressed. Tepals 5, free, equal or unequal, glabrous or hairy. Stamens normally 2-5, sometimes partly anantherous; filaments at the base united in a tube or a short cup; free part short, usually alternating with (sometimes very minute) pseudo-staminodes; anthers small, 1-celled (2-locellate); pseudo-staminodes entire, dentate or laciniate. Ovary compressed or not; ovule 1, pendulous from a long funicle; style short; stigma capitate. Utricle indehiscent, sometimes corky, falling off with the perianth and with or without the bracteoles. Seed vertical.
Annual or perennial herbs, prostrate or erect to floating or scrambling, with entire opposite leaves. Inflorescences of sessile or pedunculate heads or short spikes, axillary, solitary or clustered, bracteate. Flowers hermaphrodite, solitary in the axil of a bract, bibracteolate, bracts persistent, the perianth falling with the fruit, bracteoles persistent or not. Perianth-segments 5, free, equal or unequal, glabrous or furnished with smooth or denticulate hairs. Stamens 2–5, some occasionally without anthers; filaments distinctly monadelphous at the base into a cup or tube, alternating with large and dentate or laciniate to very small pseudostaminodes (rarely these obsolete); anthers unilocular. Ovary with a single pendulous ovule; style short; stigma capitate. Fruit an indehiscent capsule, thin-walled or sometimes corky. Seeds ± lenticular.
Herbs or subshrubs, annual or perennial. Stems prostrate, decumbent, ascending, erect, or floating, indumentum of simple trichomes. Leaves opposite, sessile or petiolate; blade lanceolate to ovate, ovate-rhombic, or obovate-rhombic, margins entire. Inflorescences axillary or terminal, sessile or pedunculate, several-flowered cylindric spikes or globose heads, without immediately subtending leaves; bracts and bracteoles scarious. Flowers bisexual; tepals 5, distinct; stamens 3-5; filaments connate basally into tube or short cup; pseudostaminodes 5, alternating with stamens; ovule 1; style 1, ca. 0.2 mm; stigma capitate or rarely 2-lobed. Utricles compressed, ovoid or obovoid, indehiscence. Seeds 1, reddish brown, lenticular or ovoid-oblong.
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.
Perennial or annual herbs or subshrubs; young stems and leaves often pubescent, but glabrous with age. Leaves opposite, entire. Inflorescences axillary or terminal, sessile or pedunculate, of various types. Flowers bisexual; tepals 5, outer 3 longer than and enclosing inner 2, glabrous inside; stamens (3)5, united below, anthers oblong or ovate, 2-locular, pseudostaminodia shorter or longer than stamens, subulate or ligulate, distally dentate to fimbriate; ovule 1, style obscure to slender, stigma capitate and globose to more or less punctate. Fruit an indehiscent utricle.
Herbs annual or perennial, ascending or creeping; stem much branched. Leaves opposite, margin entire. Flowers perfect, in sessile or peduncled heads, solitary in axils of bracts. Bracts and bracteoles persistent, membranous. Tepals 5, often unequal, membranous. Stamens 2-5; filaments connate into a tube or a cup at base; anthers 1-loculed; pseudostaminodes entire, dentate, or laciniate. Ovary globose or ovoid; ovule 1, pendulous; style short or long; stigma capitate. Utricles globose or ovoid, indehiscent, falling off with perianth. Seeds lenticular, vertical.
Fls in sessile axillary congested clusters. Per. 5-partite; fertile stamens 2-3, filaments connate at base, anthers 1-celled; style very short or obsolete, stigma us. capitate; ovules solitary, pend. from basal funicle. Utricle compressed, margins often thickened or winged; seed vertical, lenticular. Herbs, us. decumbent, with opp. lvs. About 170 spp., mainly tropical and subtropical.
Stamens 2–5, some occasionally without anthers, the filaments distinctly monadelphous at the base into a cup or tube, alternating with large and dentate or laciniate to very small pseudostaminodes (rarely these obsolete), anthers unilocular.
Flowers hermaphrodite, solitary in the axil of each bract, bibracteolate, bracts persistent, the perianth falling with the fruit, bracteoles persistent or not.
Inflorescences of sessile or pedunculate heads or short spikes, axillary, solitary or clustered, bracteate.
Annual or perennial herbs, prostrate or erect to floating or scrambling, with entire, opposite leaves.
Perianth segments 5, free, equal or unequal, glabrous or furnished with smooth or denticulate hairs.
Fruit an indehiscent capsule, thin-walled or sometimes corky, seeds more or less lenticular.
Ovary with a single pendulous ovule.
Style short, stigma capitate.
