Lithocarpus is a genus in the beech family Fagaceae, differing from Quercus in the erect male spikes. The Kew Checklist (see link below) accepts 334 species, though some other texts suggest as low as 100 species. All but one are native to east and southeast Asia; the single exception, L. densiflorus, Tanoak, being native to western North America in southwest Oregon and California. The Asian species do not have a well-known English vernacular name, though the generic term stone oak has been proposed.
Although normally included in Lithocarpus, recent genetic evidence (Int. J. Plant Sci. 162(6): 1361–1379. 2001; pdf file) suggests that the North American species is only distantly related to Asian species; it may be better transferred to a genus of its own.
They 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 (e.g. L. densiflorus).