Description from Flora of China
Cynoctonum J. F. Gmelin.
Herbs, annual or perennial, erect to creeping, branched or not. Branches terete to 4-angled. Leaves opposite, sessile or petiolate; interpetiolar stipules well developed to reduced to a transverse ridge. Inflorescences terminal and/or axillary, usually long pedunculate, 2 or 3 or more branched, branches scorpioid; bracts small, sepal-like. Flowers sessile or shortly pedicellate, 5-merous. Calyx usually parted almost to base, lobes with membranous margin. Corolla urceolate to campanulate, tube as long as to longer than lobes, lobes imbricate in bud. Stamens inserted at base to middle of corolla tube, included; filaments ± as long as anthers to shorter; anthers usually ovate, introrse, 2-locular. Ovary semi-inferior, 2-locular, with many ovules per locule. Styles cleft at base; stigma capitate or 2-cleft. Capsules 2-horned or 2-lobed, with both carpels dehiscing along ventral suture; horns or lobes erect, divergent, or curved inwards, terminating by style halves; many-seeded. Seeds small, ± subglobose to ellipsoid; seed coat smooth, reticulate, or verrucose; endosperm fleshy; embryo linear.
Seven species: Africa, America, Asia, Pacific Islands; four species in China.