Lithocarpus

Lithocarpus is a genus in the beech family, Fagaceae, commonly known as the stone oaks and differing from Quercus in the erect spikes of insect-pollinated male flowers and the short styles with punctate stigmas on the female flowers. The World Checklist (see link below) accepts 334 species, all native to Southeast Asia. About 100 Asian species of the genus were formerly treated in the genus Pasania. The North American tanoak or tanbark oak was previously included in the genus Lithocarpus (Lithocarpus densiflorus) but recent evidence, both genetic and morphological, suggests that the North American species is only distantly related to Asian stone oaks therefore tanbark-oak has been moved into a new genus, Notholithocarpus, based on multiple lines of evidence. Lithocarpus trees are evergreen trees with leathery, alternate leaves, which may be either entire or toothed. The seed is a nut very similar to an oak acorn, but with a very hard, woody nut shell (hence the genus name, from Greek lithos, stone, + carpos, seed). The nut kernel is edible in some species (e.g. Lithocarpus edulis), but inedible, and very bitter, in others. A few sections of the genus have evolved a novel type of fruit where the seed is embedded in the basal material of the fruit which becomes highly lignified and hard, lending greater mechanical protection to the seed. Several of the species are very attractive ornamental trees, used in parks and large gardens in warm temperate and subtropical areas.