The Anacardiaceae is also called the sumac or cashew family. It contains approximately 80 genera and about 600 species in mostly tropical regions but extending into temperate zones of both North America and Eurasia. In this family flowers are typically 5-merous, small and arranged in clusters. Stems and leaves often contain resinous compounds or strong-smelling volatile substances. Urushiol, a skin irritant which is produced in the genera Toxicodendron and Metopium, is probably the best known of these, causing rashes and blisters. Poison sumac, a species of Rhus, also contains urushiol. These secondary compounds probably evolved as a defense against herbivore and insect predators. A number of economically important species are in this family, including cashews, mangoes and pistachios, and another familiar member is Schinus, the pepper trees.