Annual, biennial or perennial herbs ranging from 2-180 cm. Stem branched or not, cylindrical, lineolate, angular or quadrangular, winged or not, glabrous or pubescent. Basal leaves rosulate or not, elliptic-spathulate to spathulate, oblong to lincar-oblong or obovate to cuneate, obtuse, acute or apiculate, glabrous, glaucous or pubescent, margin entire or rarely lacinulate. Cauline leaves whorled, opposite or alternate, free or connate, variable shape and texture l ike the basal leaves. Inflorescence paniculate, cymose, corymbose, solitary. Flowers pedicellate, bracteate, bracteolate, tetramerous pentmmrous, complete, bisexual, actinomorphic or slightly zygomorphic to un-equal calyx lobes. Calyx free or connate at the base rarely subpanulate or campanulate, lobes linear to narrowly ovate, obovate, spathulate to sub-spathulate, acute or obtuse, glabrous-pubescent, entire rarely ulate. Corolla white to bluish-white, pale green or dirty green, yellow, rarely reddish, rotate, rarely sub-campanulate to campanulate, lobes narrowly ovate to ovate or elliptic-oblong to ovate-oblong cuneate or obovate, acute, acuminate, caudate, apiculate, mucronate or obtuse. Glands vary in shape, fimbriate or not, 1 or 2 per corolla segment. Stamens epipetalous, free rarely connate at the base, filaments filiform, subulate, flattened, glabrous or pubescent, anthers ovate to oblong-ovate, obtuse rarely apiculate. Ovary bicarpellary syncarpous, placentation parietal, style absent or present, vary from linear-oblong to sub-oblong or orbicular to sub-orbicular. Fruit a capsule. Seeds vary from warted to annular winged to polyhedral winged, flat, rounded, ovoid or oblong.

A genus of c. 148 species.

Almost cosmopolitan but not in South America, Australia, Greenland, Iceland, Britain.