Herbs, annual or winter annual. Taproots slender to ± stout, especially proximally. Stems spreading or ascending to erect, simple or branched, terete to somewhat angular. Leaves opposite but appearing whorled, as 8-15 per axillary cluster, 2 clusters per node, connate proximally by often-prominent ridge from which stipules arise, sessile; stipules 4 per node, white, ovate to triangular, margins entire but splitting variously with age, apex obtuse to acuminate; blade 1-veined, linear or filiform, sometimes succulent, apex blunt to apiculate. Inflorescences terminal, open to diffuse cymes; bracts paired, minute. Pedicels erect to ascending, spreading or usually reflexed and sometimes secund in fruit. Flowers usually bisexual, sometimes pistillate by stamen abortion; perianth and androecium briefly perigynous; hypanthium dish- or cup-shaped, not abruptly expanded distally; sepals distinct, silvery, elliptic to nearly ovate, 2.5-5 mm, herbaceous, margins scarious, apex acute to obtuse; petals 5, white, blade apex entire; nectaries at adaxial base of broader filaments opposite sepals; stamens 5 and opposite sepals, or 10 and arising from distally tapered rim of hypanthium; filaments distinct; styles 5, distinct, filiform, 0.4-0.6 mm, glabrous proximally; stigmas 5, linear along adaxial surface of styles, obscurely papillate (30×). Capsules ovoid, opening by 5 spreading to somewhat recurved valves; carpophore absent. Seeds 5-25, blackish, circular, subglobose or lenticular and laterally compressed, nearly smooth or finely papillate, membranous, entire marginal wing often present, appendage absent; embryo peripheral, annular to spirally curved. x = 9.
Infl terminal, dichotomously branched, the pedicels reflexed; sep 5; pet 5; stamens 10 or 5; styles normally 5; valves of the capsule normally 5, opposite the sep; seeds compressed or globose, acutely margined or winged; succulent annuals with whorled lvs and scarious stipules. 5, Eurasia.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.