mistletoe, common name for the Loranthaceae, a family of chiefly tropical hemiparasitic herbs and shrubs with leathery evergreen leaves and waxy white berries. They have green leaves, but they manufacture only part of the nutrients they require. Mistletoes are aerial hemiparasites, attaching themselves to their hosts by modified roots called haustoria, with which they absorb water and food from the host. The list of hosts is varied and numerous. Mistletoes are widely used for Christmas decoration. The custom of kissing under a branch of mistletoe apparently originated among the Druids and other early Europeans, to whom mistletoe was sacred. From early times it has been associated with folklore and superstition; it was thought to cure many ills. The mistletoe most widely sold in America is Phoradendron flavescens; most popular in Europe is the "true" mistletoe, Viscum album of the related family Viscacceae, which is parasitic especially on apple trees. An American genus (Arceuthobium) with several species found along the Pacific coast is parasitic on conifers. The largest genus of the family, Loranthus, is predominantly African. The mistletoe family is classified in the division Magnoliophyta, class Magnoliopsida, order Santalales.

Any of many species of semiparasitic green plants of the families Loranthaceae and Viscaceae, especially those of the genera Viscum, Phoradendron, and Arceuthobium, all members of the Viscaceae family. V. album, the traditional mistletoe of literature and Christmas celebrations, is found throughout Eurasia. This yellowish evergreen bush (2–3 ft, or 0.6–0.9 m, long) droops on the branch of a host tree. The thickly crowded, forking branches bear small leathery leaves and yellowish flowers, which produce waxy-white berries containing poisonous pulp. A modified root penetrates the bark of the host tree and forms tubes through which water and nutrients pass from the host to the slow-growing but persistent parasite. The North American counterpart is P. serotinum. Mistletoe was formerly believed to have magical and medicinal powers, and kissing under hanging mistletoe was said to lead inevitably to marriage.

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