Plants in the brassicaceae, or cruciferae family (common names cabbage, or mustard family) have alternate leaves, hairy or not, and a clustered inflorescence of flowers with four-fold symmetry; four petals, usually white or yellow, in a cross-shape, and four greenish sepals. At the centre are (usually) six stamens and a pistil. Fruits are narrow, cylindrical pods. Many species have edible leaves. About 80 species occur in the British Isles.