EUCALYPTUS, a genus of trees of the natural order myrtaceee, suborder leptospermere, containing a large number of species, mostly natives of Australia, and which, along with trees of nearly allied genera, form one of the most characteristic features of the vegeta• Lion of that part of the world. The genus occurs also, although much more sparingly, in the Malayan archipelago. The trees of this genus have entire and leathery leaves, iv which a notable quantity of a volatile aromatic oil is usually present. The leaves, instead of having one of their surfaces towards the sky, and the other towards the earth. are often placed with their edges in these directions, so that each side is equally exposed to the light. Many of the species abound in resinous secretions, and are therefore called Gust TREES in Australia. Some of them attain a great size; some are found with trunks from 8 to 16 ft. in diameter; a plank 148 ft. in length was exhibited at the great exhibi tion of 1851. They are of very rapid growth; and their timber, when green, is soft, so that they are easily felled, split, or sawn up; but when dry, it becomes very hard. Itis used for a great variety of purposes, amongst which may be mentioned ship-building. The bark of many of the species abounds in tannin, and has become to some extent an article of commerce. Some kinds of it are said to be twice as strong as oak-bark. The hark of some is remarkable for its hardness; whilst some throw off their outer bark in longitudinal strips or ribbons, which, hanging down from (heir stems and branches, have a very singular appearance.—Among the resinous secretions of this genus is the substance called BOTANY BAY Kmo, which is used in medicine as a substitute for kino (q.v.). It is the produce of E. resinifera, a species with ovato-lanceolate leaves, known in Australia as the RED GUM TREE and IRON Baits TREE, a very lofty tree, attaining a, height of 150-200 ft. When the bark is wounded, a red juice flows very freely, and
hardens in the air into masses of irregular form, inodorous, transparent, almost black when large, but of a beautiful ruby red in small and thin fragments. Botany bay kin& is said to consist chiefly of a peculiar principle called eucalyptin, analogous to tannin. About sixty gallons of juice may sometimes be obtained from a single tree, or, in the course of a year, as flinch as five hundred pounds of kino.—E. robusta, STRINGY BARK TREE, also a lofty tree, yields a most beautiful red gum, which is found filling large cavities in its stem, between the concentric circles of wood.—E. mannifera yields, from its leaves, an exudation resembling manna, less nauseous, and of similar medicinal prop erties. It contains a saccharine substance, different from mannite, from glucose, and from all previously known kinds of sugar. Another similar exudation, from the leaves of E. dumosa, is sometimes seen spread over large districts like snow, and used by the natives as food.—The Tasmanian blue gum tree, which is one of the eucalypti, has recently acquired great reputation for its effects in drying marshy soils, and in prevent ing malarious diseases. It is extremely rapid in its growth, which may account for its drying powers; and this, in its turn, may partly account for its salubrious effects; although its camphor-like odor may also have to do with it. It has been tried with decidedly beneficial effects in the cape of Good Hope, Algeria, the Roman Cam pagna, and elsewhere. Unfortunately, it does not bear a severe winter.