Annual, biennial or perennial herbs. Stipules 0.  Leaves alternate. Flowers in racemes, usually bisexual,  hypogynous, actinomorphic. Sepals 4, free, in 2  series. Petals 4 (rarely 0). Stamens 6  (inner 4 long, outer 2 short). Ovary 2-locular.  Style 1. Stigmas 2. Fruit dry, usually a dehiscent siliqua or silicula, opening from below by 2 valves, sometimes breaking into segments transversely, sometimes indehiscent.