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MISTLETOE
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Mistletoes are typically small, green-leaved shrubs of the mistletoe family, Loranthaceae, commonly semiparasitic on trees. They are widely known for their decorative use during the Christmas season and because they can cause serious injury to certain trees. Mistletoes penetrate the bark of the host tree and attach to the conducting tissues (xylem) by suckerlike organs called haustoria, which are generally considered to be modified roots. Mistletoes contain chlorophyll and can manufacture their own food by photosynthesis, but they extract water and nutrients from the host. They were once thought to have medicinal properties, and the mistletoe of Europe, Viscum album, was believed to possess magical powers when it was found growing on oak trees.
The American mistletoes comprise about 200 mostly tropical species in the genus Phoradendron and are found from the northern United States to central Argentina. They commonly appear as bunched tufts or leafy, perennial evergreen shoots that stand out when the host has shed its leaves. A few species form long, hanging tufts or spreading, fountainlike masses. The mature fruit is commonly a translucent whitish berry, sometimes shaded with green or yellow. Birds eat the berries and spread the seeds by wiping them off their bills on to branches or by depositing them in their droppings. P. serotinum, with green, jointed stems up to 30 cm (1 ft) long and small, leathery leaves and yellow flowers, is the common American Christmas mistletoe. Western American Indians used to boil the berries of certain species as food, and a tea made from the leaves was believed to have contraceptive and abortive qualities. Mistletoe may be toxic to browsing livestock, however, and the raw berries of Eastern species have proved fatal to children.
The dwarf mistletoes, Arceuthobium, attack and may kill conifer trees. They have small, scalelike leaves and vary in size from 13 mm to 15 cm (0.5 to 6 in).
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