Annual or perennial herbs, sometimes shrubby, usually hairy. Leaves opposite, mostly sessile, entire, exstipulate. Flowers white, mostly in terminal, dichasial cymes. Sepals 5 (4), free. Petals 5 (4), rarely 0, emarginate to 2-fid, rarely entire. Stamens 10 (8), sometimes 5 or less. Hypogynous disk present. Ovary 1-celled; styles 5, sometimes 3-4. Capsule scarious, usually longer than calyx, cylindrical or oblong, dehiscing by short teeth the number of which is twice that of styles. Seeds many, globular or reniform, mostly tuberculate; embryo almost annular.