Oak, the English name for the genus Quercus which forms the type of the sub-order Quercineae of the order Cupuliferae, and includes nearly 300 species, mostly large trees, though in some cases mere shrubs, natives of temperate regions and moderate altitudes in the northern hemisphere. Their leaves are scattered, simple, and pinnately-veined, and have deciduous stipules. The species of warmer regions are evergreen, and have nearly entire leaf-margins, whilst the deciduous leaves of northern species are sinuate or cut. They are monoecious, bearing their male flowers in loose catkins and the female ones solitarily. The former have each a 5-7-lobed calyx and from 5 to 12 stamens; and the latter a 3-8-lobed calyx, a three-chambered ovary, and three styles. The ovary contains two ovules in each chamber, but becomes by abortion one-chambered and usually one-seeded. The fruit or acorn (q.v.), an inferior nut with a leathery exterior and enclosed below in a woody cupule or cup, is characteristic. This cup is formed by an outgrowth from the peduncle bearing numerous imbricate bracts. Q. Robur, one of the largest species of the genus, though known as the British Oak, ranges from Mounts Atlas and Taurus to lat. 63° N., about the limit of wheat-cultivation in Europe, and was reverenced for its fruit and timber alike by Greek, Roman, Celt, Saxon, and Norseman. Vast oak-forests covered central Europe at the dawn of history, and it is still a prevalent species in south Russia, Germany, France, and England. Its wood, stained black and known as bog-oak, is found in prehistoric peat-bogs and in submerged forests. It was the favourite timber for ship-building and for domestic architecture among the Greeks and Romans. The tree sometimes reaches 100 feet in height and nearly 50 feet in girth, producing sound wood for 200 years; and, even when hollow, may retain its vitality for two or three centuries longer. The timber weighs about 50 lbs. per cubic foot or, in very hard slow-grown wood, nearly 60 lbs. When finely-grained, it is valued for furniture and carving. The bark has long been a valuable product, and until recent years was the chief tanning material of the world. In trees from 20 to 30 years old it contains from 7 to 10 per cent. of querci-tannic acid. An immense variety of insects feed upon the oak, some of them producing galls, such as the large spongy and rosy oak-apples and the small discoid oak-spangles on the leaves. Next in importance to Q. Robur among European oaks is the Turkey Oak, Q. Cerris. The evergreen or holm (holly) oak of southern Europe, Q. Ilex, grows to smaller dimensions, but has very dense wood. Q. Suber, whence we derive our supply of cork (q.v.), is a similar species with a more western distribution. The large thick acorn-cups of the Levantine Q. AEgilops and Q. Vallonea, with reflexed scales, are rich in tannin, and are imported under the name of valonia, their young acorns - also used for tanning - as camata or, when still younger, as camatina. Q. infectoria produces the Aleppo galls, of which we import about 1,000 tons annually for ink-making and dyeing. Of the numerous oaks of America - most of which are valuable as timber, though less durable than Q. Robur - the chief is the white oak, O. alba; but several, such as Q. rubra and Q. coccinea, are grown in England, as scarlet oaks for the autumn beauties of their leaves. We import over 100,000 loads of oak-timber annually, chiefly from the Continent and from North America, and about 30,000 tons of bark, chiefly from Belgium, in addition to a home supply of the latter of nearly ten times that amount.