spurge

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spurge

(spûrj), common name for members of the Euphorbiaceae, a family of herbs, shrubs, and trees of greatly varied structure and almost cosmopolitan distribution, although most species are tropical. In the United States the family is most common in the Southeast.

Euphorbias

Many plants of the spurge family have reduced fleshy leaves, in particular the vast Euphorbia genus of approximately 1,600 subtropical and warm-temperate species. These cactuslike plants, comprising most of the species commonly called spurge, have spiny, jointed stems and are among the most common Old World desert succulents. The euphorbias and the cacti illustrate the biological phenomenon of convergent evolution, in which unrelated groups of organisms, subject to the same environmental pressures, gradually develop similar structures. The euphorbias exhibit another family trait: "naked flowers" (i.e., flowers lacking petals and sometimes sepals) that are enclosed in a bract envelope, from which they emerge during the flowering period to permit pollination.

Many species are cultivated for their brilliant, showy bracts as well as for their frequently colorful foliage. These include snow-on-the-mountain (E. marginata), native to the United States; the cypress spurge (E. cyparissias), a favored cemetery plant that was introduced from Europe and naturalized; the scarlet-bracted greenhouse plant crown-of-thorns (E. splendens), native to Madagascar; and the poinsettia (for J. R. PoinsettPoinsett, Joel Roberts
, 1779–1851, American diplomat and politician, b. Charleston, S.C. In 1810 he was sent as a special commissioner to South America to investigate political conditions of the countries struggling for independence.
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), an ornamental shrub native to Central America. The poinsettia (E. pulcherrima), whose several species are sometimes considered a separate genus (Poinsettia), is a popular Christmas decoration with its large rosettes of usually bright-red bracts.

Other Spurges and Their Uses

Many spurges are of great economic importance as a source of food, drugs, rubber, and other products. The sap of most species is a milky latex, and the source of a very large part of the world's natural rubberrubber,
any solid substance that upon vulcanization becomes elastic; the term includes natural rubber (caoutchouc) and synthetic rubber. The term elastomer is sometimes used to designate synthetic rubber only and is sometimes extended to include caoutchouc as well.
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 is the latex of the Pará rubber treePará rubber tree
, large tree (Hevea brasiliensis) of the family Euphorbiaceae (spurge family), native to tropical South America and the source of the greatest amount and finest quality of natural rubber.
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. Pará rubber and several other latexes also come from plants of the spurge family. The tropical American Manihot genus includes the cassavacassava
or manioc
, name for many species of the genus Manihot of the family Euphorbiaceae (spurge family). The roots, which resemble sweet potatoes and are eaten in much the same way, yield cassava starch, a staple food in the tropics.
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, the source of tapioca and the most important tropical root crop next to the sweet potato.

Other valuable commercial products of this family are castor oilcastor oil,
yellowish oil obtained from the seed of the castor bean. The oil content of the seeds varies from about 20% to 50%. After the hulls are removed the seeds are cold-pressed.
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 and tung oiltung oil,
oil obtained from the seeds of a tropical tree, the tung tree (Aleurites fordii) of the spurge family, and from seeds of some related species, all from Indomalesia or W Pacifica. It is known also as China wood oil and nut oil.
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, expressed from the seeds of Ricinus communis and Aleurites fordii respectively. The castor beancastor bean,
bean produced by Ricinus communis, a plant of the spurge family, widely cultivated as an ornamental. Moles die when they eat the roots. It has long been used as an ordeal poison in parts of Africa.
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, the source of castor oil, is native to tropical Africa, where it grows as a tree, but is now widespread and is sometimes cultivated in temperate regions as an annual ornamental. The tung tree, indigenous to E Asia and Malaysia, is the only important plant of the spurge family cultivated commercially in the United States. The candlenut tree (A. moluccana) and the Japanese wood oil tree (A. cordata), of the same genus as the tung tree, also yield oils, as does the Chinese tallow tree (Sapium sebiferum), a source of grease for candles and soap.

Various spurges provide medicines, dyes, oils, and other products; primitive peoples utilized the poisonous saps of other spurges on arrow tips and to poison fish. The presence of poisonous substances in many euphorbias and in a number of other spurges has led these to be classed as noxious pests, especially when they grow as weeds on livestock ranges.

Classification

Spurge is classified in the division MagnoliophytaMagnoliophyta
, division of the plant kingdom consisting of those organisms commonly called the flowering plants, or angiosperms. The angiosperms have leaves, stems, and roots, and vascular, or conducting, tissue (xylem and phloem).
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, class Magnoliopsida, order Euphorbiales, family Euphorbiaceae.

spurge

any of various euphorbiaceous plants of the genus Euphorbia that have milky sap and small flowers typically surrounded by conspicuous bracts. Some species have purgative properties