A large family, widely distributed. Both the English and Latin names are appropriate, for the watery juice of these plants is pungent, like mustard, and the flowers spread out their four petals in the form of a cross. They are herbs, the leaves alternate or from the root, usually with no leaf-stalks. The flowers have four petals, with claws; four sepals, the two outer ones narrow, apt to drop off; six stamens, two of them short. The ovary is superior, usually with a single style and stigma, and usually develops into a pod, divided in two by a transparent partition, which remains after the pod has opened from below; in some kinds the pod remains closed. The flowers generally grow in clusters and though they are often small they produce honey and so are frequented by bees and flies. The family is easily recognized by the four petals and in most species by two stamens being shorter than the others, but the flowers are so much alike that the various kinds have to be determined by examining the fruit. Radish and Horse-radish, Mustard and Water-cress all belong to this family, as well as many familiar garden flowers, such as Sweet Alyssum, Candytuft, Rockets, and Stocks, and many are common weeds, such as Peppergrass and Shepherd's Purse.

There are several kinds of Dentaria, smooth perennials, with rather large white or pink flowers and tuberous root-stocks.