Guar, or clusterbean, Cyamopsis tetragonoloba L. Taub is a droughttolerant annual legume that was introduced into the United States from India in 1903. Commercial production of guar in the United States began in the early 1950s and has been concentrated in northern Texas and southwestern Oklahoma. The major world suppliers are India, Pakistan and the United States, with smaller acreages in Australia and Africa. In the early 1980s, Texas growers were planting about 100,000 acres annually. They harvested about half of the planted acreage and plowed the rest under as green manure. Unlike the seeds of other legumes, the guar bean has a large endosperm. This sphericalshaped endosperm contains significant amounts of galactomannan gum 19 to 43 of the whole seed, which forms a viscous gel in cold water. Guar gum is the primary marketable product of the plant. India and Pakistan export much of their guar crop to the United States and other countries in the form of partially processed endosperm material. World demand for guar has increased in recent years, leading to crop introductions in several countries. Like other legumes, guar is an excellent soilbuilding crop with respect to available nitrogen. Root nodules contain nitrogenfixing bacteria, and crop residues, when plowed under, improve yields of succeeding crops.

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