Man used leguminous plants to enrich the soil centuries before he knew what made them useful. Records from the oldest civilizations of Egypt and eastern Asia demonstrate the ancient use of various Old World beans, peas, vetches soybeans, and alfalfa. One of the early Greek botanists, Theophrastus, in summarizing much that had been learned up to his time, which was the third century before Christ, wrote of leguminous plants “reinvigorating” the soil and stated that beans were not a burdensome crop to the ground but even seemed to manure it. The Romans laid emphasis on the use of leguminous plants for green manuring; they also introduced the systematic use of crop rotations, a practice that was forgotten for a time during the early Middle Ages.
In the Americas as well as the Old World, there was a well-developed native agriculture that had not neglected the indigenous legumes. When Columbus reached the West Indies, lie was much impressed by cultivated fields of corn, sweetpotatoes, cassava, and peanuts, the last a legume. The early European immigrants found the Indians of the Atlantic coast raising native legumes with their corn. In the Southwest, beans such as the tepary bean were cultivated, and wild leguminous seeds were ground and eaten by the Indians, the mesquite being a staple food of many tribes.
Legumes are second only to the cereal grasses as sources of human food and animal forage. In the United States the leguminous forage crops are well represented, and food legumes such as peas, beans, cowpeas, soybeans, and peanuts are extensively grown. Sources of food little known to us but important in other parts of the world include the chickpea of southern Europe; the horsebean, much grown in England for forage as well as for its seeds and now grown in our Pacific Coast States; the nutritious lentil of the Mediterranean countries; the pigeonpea widely cultivated in the Tropics as a food and forage crop; the hyacinth-bean of the Tropics; the tropical jackbean, grown for forage in the southern United States; and the velvetbean, cultivated in the Tropics for its edible seeds and now grown in the southern United States.
The honeylocust, carob, algarroba or mesquite and the tropical tamarind are leguminous trees important as food for man and animals. Others of this category are the raintree of tropical America, the nittas of West Africa, and the ingas, especially Inga edulis of Panama and Peru.
The legumes also furnish other products valuable to man. Numerous gums and tannins are obtained from African and Australian Acacias. Bark from a species of Cassia is the chief source of tannin in India, and the divi-divi yields tannin in the American tropics. Some commercial resins come from legumes. African copals, for instance, are from special of Copaifera and Daniella. Gums and resins are also obtained from species of American Prosopis, African and Indian Pterocarpus, and South American Myroxylon. Zanzibar copal, hardest of all resins save amber, comes from the leguminous tree, Trachylobium verrucosum.
Valuable dyes are derived from legumes, including indigo from Indigofera and haematoxylon or logwood from Haematoxylon cantpechianum, a tree of Central America. The most important brown dye, catechu, comes from the Indian Acacia catechu. The first red dyewood to be discovered was a legume, the sappanwood of the Asiatic tropics. When this wood was introduced into Europe it was called “bresel wood,” and when the Portuguese discovered a similar dyewood, now called brazilwood, in South America, they naturally gave it the same name, “bresel,” whence came the name of the country, Brazil. Other red dyes come from the West African barwood or camwood and the East Indian red sandalwood.
Numerous valuable timber trees are numbered among the legumes, such as the American cocobola and Brazilian rosewood, the Asiatic sissoo, and Indian rosewood, all in the genus Dalbergia. Timbers of the South American rain forests include, the giant trees purple heart, South American locust, and mora. Other leguminous trees useful for their wood are the Asiatic acle or pyinkado, the Australian blackwood acacia, now being grown in California, American ebony, and our own Kentucky coffeetree, black locust, and honeylocust.
Further interesting useful products of the Leguminosae are gum tragacanth, obtained from a thorny shrub of southeastern Europe and western Asia; the drug senna from Egyptian and Arabian species of Cassia; insecticides and fish poisons from East Indian species of Deriis and the South American Lonchocarpus; and vanilla substitutes from South American tonka beans of the genus Dipteryx. Fatty oils are obtained from soybeans, peanuts, and the pongam of India. A valuable perfume oil is obtained from the sweet acacia or cassie, Acacia farnesiana a spiny shrub of the West Indies that also occurs along the southern border of the United States. The Bengal kino was used in 250 A. D. as a host for the lac insect, from which at that time a red dye was obtained. Since the sixteenth century, the resinous excretions of the insect have been more extensively used in the manufacture of shellac. Acacia arabica and the pigeon-pea are other legumes that furnish hosts for the lac insect, propagated mostly in India.
The legumes furnish only one spice, namely fenugreek, the seeds of which are used in curries; au extract of the seeds, together with other aromatic substances, is used in making an artificial maple flavoring. They include only one valuable fiber plant, the sunn-hemp of India which has been cultivated for centuries. Hemp sesbania, or Colorado River Hemp, however, was used by the Indians of the southwestern United States as a source of fiber. Licorice is obtained from a legume of southern Europe and central Asia, the fibers of which have been used in making wallboard. A few legumes such as licorice, ratany, and goatsrue have some medicinal value; many others rank among our most highly ornamental plants, and legumes are of great importance for honey production.
Today in the United States, legumes are widely used for green manure, forage, and food. They are useful as green-manure crops because they have the capacity to add nitrogen as well as organic matter to the soil. Their forage value is indicated by the fact that alfalfa is the most important of all forage crops. Other legumes valuable as forage are clovers, cowpeas, kudzu, lespedeza, peanuts, velvetbeans, soybeans, field peas, and vetches. The value of clovers in. pasture mixtures is well recognized, and other legumes are frequently pastured. Although most legumes are deficient in fermentable sugars, alfalfa is sometimes used as ensilage, especially when molasses is added. With the growing consciousness that the soil must possess a vegetal cover to prevent erosion, legumes are being used more and more for erosion control. They are grown as cover crops, in strips alternating with clean-tilled crops, and in grass-legume mixtures on steep land retired from cultivation.
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