An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Rosidae of the class Magnoliopsida (dicotyledons). The order consists of 10 families and about 2000 species. The largest families are the Loranthaceae (about 900 species), Santalaceae (about 400 species), Viscaceae (about 350 species), and Olacaceae (about 250 species). A few of the more primitive members of the Santalales are autotrophic, but otherwise the order is characterized by progressive adaptation to parasitism, accompanied by progressive simplification of the ovules. In the Loranthaceae the ovules have no integument and are embedded in the large, central placenta. Some other families have a free central placenta with pendulous, terminal ovules; in any case there are only a few ovules, in contrast to the very numerous ovules of the Rafflesiales. Some members of the Santalales, such as sandalwood (Santalum album, a small tree of southern Asia), are rooted in the ground and produce small branch roots which invade and parasitize the roots of other plants. Others, such as mistletoe (Viscum and other genera of the Viscaceae), grow on trees, well above the ground.