GUAYULE

(Parthenium argentatum), rubber-containing desert shrub of the family Asteraceae, native to the north-central plateau of Mexico and the Big Bend area of Texas. It has small white flowers and narrow silvery leaves that alternate along the stem. Prehistoric Indians are believed to have obtained rubber by chewing the bark of the plant. The modern method is to macerate the shrub mechanically. Rubber was extracted in Mexico from wild plants during the early 20th century, and vigorous efforts were made to cultivate guayule in the southwestern United States during World War II. Commercial production of guayule rubber ceased soon after the end of the war, but Mexico kept working on its development, and research plantings have been continued in Spain, Turkey, and the United States.