This publication is one of a series preliminary to a manual of U. S. Leguminosae. The four genera presented include five native and five introduced species in the southern U. S. Four introduced genera reported for the U. S. are rejected. The treatment comprises generic descriptions, keys, and taxonomic and nomenclatural judgements. One new combination; Lysiloma microphylla var. thornberi (Britt. & Rose) Isely.