The size and characteristics of the family Leguminosae are outlined, with a key to the 3 subfamilies. Rhizobia are characterized in pure culture and various aspects of Rhizobium-plant associations are discussed, as well as the concept of cross inoculation grouping and its significance. An elementary account of nodule formation and types is given, and reasons for nodule absence and the inherent inability of certain spp. to nodulate are discussed. The main body of the work consists of synopses of 750 genera arranged alphabetically. Each is described within its tribe and subfamily, in accordance with accepted classification systems. Conserved genera and type spp. are designated and the etymology of the generic name is given. For each genus information is given on the number of spp. in the genus, endemic geographical areas and basic ecological habitats, uses and economic importance. Emphasis is given to information or discussion of nodulation reports (nodule descriptions, histology, crop yield increases and cross inoculation). Known nodulated and nonnodulated spp. are listed for each genus and the nodulation data are summarized in tabular form for each subfamily.<new para>ADDITIONAL ABSTRACT:<new para>The main body of the work consists of synopses of 750 leguminous genera arranged alphabetically. Pertinent information, including the number of species in the genus, endemic geographic areas and basic ecological habitats, uses, economic importance, and distinguishing or singular characteristics of certain species, is supplied. Emphasis is given to information or discussion of nodulation reports, such as nodule descriptions, histology, crop-yield increases, and cross inoculation. Each generic synopsis concludes with alphabetical listings (when available) of known nodulated and nonnodulated species, together with the areas of examination and authorities for the report. A bibliography listing nearly 1,500 titles is included