This National Academy of Sciences report describes plants of the family Leguminosae, all of them greatly underexploited. Some are extensively used in one part of the world but unknown elsewhere; others are virtually unknown to science but have particular attributes that suggest they could become major crops in the future; a few are already widespread but their possibilities are not yet fully realized.Most of the plants described in this book have the capacity to provide their own nitrogenous fertilizer through bacteria that live in nodules on their roots; the bacteria chemically convert nitrogen gas from the air into soluble compounds that the plant can absorb and utilize. As a result, legumes generally require no additional nitrogenous fertilizer for average growth. This is advantageous because commercial nitrogenous fertilizers are now extremely expensive for peasant farmers. This report demonstrates how farmers in developing countries, by using leguminous plants, can grow useful crops while avoiding that expense. However, the plants to be discussed here should be seen as complements to, not as substitutes for, conventional tropical crops.