Evergreen or deciduous trees or shrubs. Male flowers in loose slender catkins; perianth 5- to 10-lobed; stamens indefinite, with slender exserted filaments. Female flower solitary, perianth 3- to 8-lobed, ovary 3-celled, styles 3. Fruit ovoid or oblong, 1-seeded, seated in a cupule of imbricated scales. There are about 250 species belonging to this genus, none of which occur south of the equator. The name is of classical Latin origin.

1. Q. Robur. Common Oak. - This is the most majestic of our indigenous trees, though in height it is usually exceeded by the Elm and other species, very rarely attaining to 90 or 100 feet. There are two extreme forms which have been classed as species, but intermediate connecting varieties have since been discovered. Q. R. sessiliflora has petiolate leaves and nearly or quite sessile acorns; Q. R. pedunculata has sessile leaves and pedunculate acorns. This species has a wide range of distribution in Europe and Asia. There are several slight varieties, and a few sufficiently distinct to plant in large collectons, such as pendula, heteruphylla, pectinata, varieyata, and picta, the latter with pink, white and green foliage.

2. Q. Cerris. Turkey Oak. - A very handsome deciduous South European species of more rapid and symmetrical growth than the native Oak. The leaves in the common form are usually smaller and more finely lobed and sharply toothed, and the fruit is not ripened till the second year. The bracts forming the cup or involucre of the long narrow acorn are long, narrow and spreading. This is the only exotic deciduous species commonly planted, and of this there are many fine specimens in various parts of this country. Although the leaves change to brown in Autumn, they persist during a greater part of Winter. There are several varieties, including a very beautiful silver-variegated one, and another with large almost evergreen foliage called Fulhamensis.

3. Q. cocoinea. Scarlet Oak. - A highly ornamental species with large deciduous oblong-oval sinuately lobed petiolate glabrescent leaves about a foot long. Acorn small, ovoid or globular, half-immersed in a scaly involucre. This is a hand-some fast-growing large tree of pyramidal outline, and especially conspicuous in Autumn when the foliage changes to a bright scarlet. It is a native of North America, and less valuable as a timber-tree than many other species.

Q. alba, White Oak, Q. macrocarpa, Bur Oak, Q. rubra, Red Oak, and Q. tinctoria, Yellow-barked Oak, are other North American ornamental and useful species, but they are almost unknown in this country. Q. AEgilops, the Valonia Oak, furnishes the very large acorns imported from the South of Europe into this country for tanning purposes. It is rarely seen, except in a very small state, in this country.

4. Q. Ilex. Evergreen Oak. - The only species of the evergreen section commonly seen. It is variable in foliage from narrow-lanceolate to oblong or nearly rotundate, and more or less prickly toothed or quite entire. The acorns are small and half-immersed in the closely imbricated cup. Native of the South of Europe.

Q. Suber, the Cork Oak, is very near the last in general aspect, and is equally variable in foliage, but the leaves have longer petioles, and the bark, instead of being smooth, is deeply furrowed and corky. Q. occidentalis is often confused with the true Cork Oak, but the latter ripens its acorns in one season, whereas the former requires two to bring them to maturity.