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Leguminosae The third largest family of flowering plants, comprising trees, climbers, shrubs, and herbs, some of which are aquatic. Innumerable species are of great economic importance for timber, fodder, drugs, or food. The leaves have stipules and are usually pinnate. Many species have root nodules containing nitrogen-fixing bacteria. The inflorescence is basically racemose. The flowers are regular or zygomorphic, basically with 5 sepals and petals, the sepals often united. Typically there are 10 stamens (but many in Mimosoideae) which are sometimes fused. The ovary is superior, with a single carpel. The fruit is a pod, usually several-seeded, and usually dehiscent. There are 3 subfamilies, distinguished by their different flower construction: Caesalpinoideae and Mimosoideae are mainly tropical; Papilionatae has many temperate species and many herbs. There are 657 genera, with about 16 400 species, of cosmopolitan distribution.