Annual or perennial herbs, sparse subshrubs. Stem nodes are usually enlarged and articulated. Simple leaves opposite, sparsely alternate or whorled, entire, more or less connate at the base; Stipules membranous or absent. Flowers are radially symmetrical, bisexual, sparsely unisexual, arranged in cymes or cymes, sparsely solitary, with a few racemes, heads, pseudo-cymes or umbels, and sometimes cleistogamy; Sepals 5, sparse 4, herbaceous or membranous, persistent, imbricate or United into a tube; Petals 5, sparse 4, claw-free or claw-free, petals entire or completely split, usually there are 2 or scaly corollas between claws and petals, and few petals; Stamens 10, two rows, sparse 5 or 2; The pistil is 1 and consists of 2-5 syncarps. The ovary is superior, with 3 cells or 1 cell at the base and 3-5 cells at the upper part. It has a central placenta or a basal placenta with 1 to many ovules. Styles (1)2-5, sometimes the bases are combined and sparse to form a single style. The fruit is a capsule, oblong, cylindrical, ovoid or spherical, with shell, membrane or paper, teeth or valves at the top, the number of cracks is the same as or twice as that of the style, and there are few berries, irregular cracks or achenes; Seeds curved, mostly or rarely, 1, kidney-shaped, ovoid, peltate or round, slightly flat; The hilum is usually located in the concave part of the seed, sparsely peltate; The seed coat is papery, with several layers of semi-circular particles, short lines or tumor-like protrusions centered on the hilum, and the sparse surface is nearly smooth or the seed coat is spongy; Seed ridges are grooved, obtuse or sharp, with sparse fringed teeth or wings; The embryo is annular or semicircular, surrounding the endosperm or erect, and the endosperm inclines to one side; Endosperm silty.