Annuals, to 50 cm tall. Roots fibrous. Stems succulent, erect, much branched from base; branches slender, longitudinally striate, glabrous. Leaves sometimes scalelike, gradually decreasing in size upward, sessile, lanceolate to subspatulate-lanceolate, to 2 cm, base amplexicaul and generally narrowly attenuate, margin entire, apex acute to obtuse; veins inconspicuous. Pedicel slender, to 1 cm. Calyx campanulate, ca. 2 mm, parted to slightly beyond middle; lobes 5, apex obtuse. Corolla white, rose, or pale purple, ca. 2 X as long as calyx; lower lip lobes spreading flat; upper lip erect, short. Stamens glabrous. Capsule globose, ca. 2 mm in diam. Seeds ovoid-oblong; seed coat reticulate.
Erect, usually simple, aquatic herb, up to 300 mm tall. Stem leaves ovate, 10-50 mm long, lower leaves oblanceolate, 10-30 mm long. Lowermost flowers in inflorescence sessile and cleistogamous. Perfect flowers pedicellate, pedicels 5-10 mm long. Fruit globose or ovoid, 1.5-2.0 mm long. Flowers white or pale mauve.