Herbs, annual, caulescent, usually distinctly pubescent, from fibrous roots. Stems leafy, erect to decumbent, branching distally. Leaves mostly opposite or whorled, sessile; blade broadly linear, unlobed. Inflorescences axillary or terminal, 1-flowerd; bracts absent; bud nodding. Flowers: receptacle slightly expanded beneath calyx; sepals 3, with overlapping, loosely connivent flaps; petals 6, occasionally more on robust specimens; stamens many in several series; filaments dilated distally; pistil 6-many-carpellate; ovary with each carpel forming almost closed locule with 4-24 ovules; stigmas 1 per carpel. Capsules erect or sometimes nodding, carpels dissociating, each torulose and breaking transversely into 1-seeded segments, sometimes also releasing free seeds. Seeds usually many, aril absent. x = 6.
w United States
Species 1 (1 in the flora).