THE invasion of mesquite into large areas of range and pasture lands in the Southwest has been progressing for many years, but only within recent years has it become of major concern to livestock raisers. In general mesquite is considered undesirable because it has reduced the carrying capacity by forming dense jungles of brush on once productive lowlands that have deep soils and favorable moisture conditions. Mesquite has hindered greatly the managing and caring for livestock and the use of desirable range improvement practices. In 1896 J. G. Smith (15), an agrostologist stationed at Abilene, Texas, called attention to the hardy, aggressive nature of mesquite and rather accurately predicted the mesquite problem we face today. In Texas alone recent surveys by the Soil Conservation Service (2) show that mesquite occurs on 55 million acres of grassland in 113 counties and that moderate or dense stands occupy approximately 30 million acres.