RELATIONSHIPS OF THE OAKS—THEIR DISTRIBUTION IN SPACE AND TIME.
The oak is a member of a very large and ancient group of dicotyledonous flowering plants, embracing the beeches, chestnuts, hazel-nuts, etc., and many other forest trees of the Northern Hemisphere.
The number of species of oaks (Quercus) is very large, probably more than 300, of which the majority belong to North America, Europe, China, Japan, and other parts of Asia. There are none in Africa south of the Mediterranean region, nor in South America orA ustralasia. Some remarkable species are found in the Himalayas, and many in the Malayan Archipelago.
The various species of the genus Quercus are arranged into groups according to differences in the form and arrangement of the scales of the cupule, the characters of the leaves, and certain peculiarities in the acorns. Many oaks, especially those of warm countries, for instance, are "evergreen," with hard, leathery leaves, quite unlike the leaves of our common British oak.
The latter is denominated botanically as Quercus