(Leguminosae, Fabaceae), a family of dicotelydonous plants, widely distributed in all regions of the earth. Sometimes three closely related families are united under the name of Leguminosae: Papilionaceae, or Fabaceae; Caesalpiniaceae; and Mimosaceae.

The leaves of the legumes for the most part are regular, as a rule with stipules and complex leaves. The flowers are usually in clustered, eared, or head-shaped racemes, generally zygomorphic (so-called butterfly-shaped), very rarely actinomorphic. The calyx is gamophyllous. There are five petals; the upper, or hind, one is the largest (the so-called flag, or sail); the two smaller side petals form the so-called oars or wings; and the two even smaller ones form the so-called boat or keel. Occasionally the corolla is reduced. The stamens (ten, very rarely nine to five) are all accreted, or only nine are, with one remaining free. The pistil comes from one carpel, the ovaries are elevated, and the fruit is a bean.

Approximately 500 genera and 12,000 species of annual and perennial grasses, semishrubs, shrubs, lianas, and, more rarely, trees (generally in the tropics) are related to the Leguminosae. There are more than 60 genera and 1,800 species in the USSR. The roots of legumes form distinctive tubers, containing leguminous bacteria capable of fixing atmospheric nitrogen. Together with the grains, legumes are the most nutritious field grasses. Clover, alfalfa, vetch, lupine, sainfoin, vetchling, serradella, and others have especially high feed value and are important in grassland crop rotation. The protein-rich seeds of the Leguminosae, such as peas, beans, soybeans, many varieties of the French bean, lentils, chick peas, peanuts, blue beans, and others, are widely distributed food products. The oils of peanuts, soy beans, and other species also go into food and are used for technological purposes.

There are many species among the Leguminosae which give products used in technology, such as the tragacanth Astragalus, which produce gum, and the valuable balsam trees (species of the genus Myroxylon). Some legumes supply costly woods—so-called rosewood (species of the genus Dabbergia) and African mahogany (D. melanxylon). Red sandal wood (Pterocarpus santalinus) and the woods of other species of Pterocarpus are used to make costly furniture, as well as to get resin for films. There are also dyes among legumes—indigo, genistin, and others. Licorice is a valuable industrial and medicinal plant. Of other medicinal plants, the most well-known are Thermopsis, restharrow, sweet clover, and Sphaerophysa, as well as the highly poisonous calabar bean (Physostigma venenosum). Certain Leguminosae (derris, Lonchocarpus, and others) are poisonous and are used as insecticides. Legumes, including the poisonous species (Thermopsis and sophora) can be considered weeds in meadows. Many legumes are widely used as decorative plants (sweet peas, lupine, wisteria, robinia, caragana, and others).