_Quercus_ (Oak, Fig. 335). Catkins simple. ♂-catkins long, thin, _pendulous_, few-flowered. ♀-catkins erect; the cupule is _cup-like_, _entire_, and encloses only the base of the solitary nut (“acorn”).--~The ♂-flower has a similar construction to that of the Chestnut. The ♀-catkin has not more than 5 flowers (single-flowered dichasia, in which _only the central flower is developed_). The scales on the cupules are no doubt leaf-structures in this case also. According to another theory, the scales are hair-structures; they arise on the internal face of the young cupule apparently in descending, but really in ascending order. The rim of the cupule gradually expands. In the ♀-flower (Fig. 335) the loculi of the gynœceum, together with the ovules, are not developed until _after_ pollination.--The leaves in all cases have a divergence of 2/5; the lowermost leaves on the shoots are reduced to stipules which serve as the bud-scales (5 rows). The laminæ are conduplicate, as in _Corylus_, and the external side is the broadest. The cotyledons are fleshy and remain underground. 200 species.--_Pasania_ (100 species).~ [Illustration: FIG. 335.--_Quercus_: _A_ ♀-flower in its cupule (mag.); _B_ longitudinal section through _A_, showing cupule, perianth, and inferior ovary.] [Illustration: FIG. 336.--Fruit of _Quercus_.] 368 species, in temperate climates, especially in Europe and N. America. Authenticated forests have been found in the Oligocene. The Beech has one species, _Fagus sylvatica_, in Europe; it is a most important forest tree (in Denmark the most important) and reaches its most northern limit near Alvesund in Norway (60° N.L.), its northern boundary line passing from Alvesund in a zig-zag line through Ludwigsort, south of Königsberg, in Prussia, towards the Crimea. According to Steenstrup and Vaupell, the Beech did not make its appearance in Denmark until a comparatively recent time, the Oak then being partially supplanted. Other species of Beech are found in N. America and Japan. Several species of _Nothofagus_ occur in the South West of S. America, and in the colder regions of the southern hemisphere. The Oaks grow especially in temperate regions, _e.g._ in Western Asia, N. America, and the mountains of Mexico. Evergreen species are found in Tropical Asia, Himalaya, Japan and the Mediterranean region. In this country there is one species of Oak (_Q. robur_), of which there are three varieties (_Q. pedunculata, intermedia, sessiliflora_). The Eating-chestnut is found in the South of Europe, but is cultivated in the midland and southern counties of England.--USES. The wood of these trees is very useful as timber. The wood of _Q. tinctoria_ has a yellow colouring matter (Quercitron-wood). The bark of the Oak contains a large quantity of tannic acid, and is used for tanning; for this purpose also the cupules of _Q. vallonea_, _ægilops_, _græca_,