(Fabaceae) A large family of dicotyledonous plants, commonly called the pea family, and containing about 17 000 species in about 700 genera. Legumes usually have pinnately compound leaves, and root nodules containing nitrogen-fixing bacteria of the genus Rhizobium. The inflorescence is usually a raceme and the individual flowers have five fused sepals and five petals often arranged in a shape fancifully resembling a butterfly (see also standard
), hence the name of the largest subfamily, Papilionoideae. The three subfamilies are sometimes classified as families; Mimosaceae, Caesalpiniaceae, and Papilionaceae. The fruit is typically a pod or *legume
. Many of the Papilionoideae are important food crops, e.g. Phaseolus and Vicia (various kinds of bean), Pisum sativum (pea), Lens culinaris (lentil), and Arachis hypogea (peanut). Others such as Trifolium (clovers) and Medicago sativa (lucerne), are used for forage. Ornamentals include Wisteria and Lupinus.