FAGACEAE, in botany, the beech family; dicotyledonous plants, most of the 35o species being trees. The family includes five genera, the most important being Fagus (beech, q.v.), Quercus (oak, q.v.) and Castanea (chestnut, q.v.). The flowers are borne in catkins in the axils of the leaves, and are unisexual. The pollen is wind-borne. The fruit is a one-seeded nut.