Eucalyptus, which includes upward of 150 species, holds the first place among these exotic plants. The Eucalypti belong to the natural order Myrtacæ, and are indigenous almost exclusively to Australia and Tasmania. They are distinguished for a high development of the phenomenon known as heteromorphism—the same plant assuming a perfectly different habit at different stages of its growth. The species with which we are just now concerned, the Eucalyptus globulus, presents two very distinct forms: when the plant is young, the leathery leaves are opposite and sessile; this is a sort of larval state—the plant is not yet mature, and cannot produce flowers. But in the adult state the leaves are pedunculate and alternate, and then the plant flowers and bears fruit. This polymorphism, however, does not occur to the same extent in all species of the Eucalyptus, and it is almost altogether wanting in E. cordata.
The honor of having discovered the Eucalyptus globulus belongs to a French scientist, Labillardière, the botanist, who accompanied the Chevalier d'Entrecasteaux on his expedition in the year 1791, to search for the lost crew of La Pérouse. Labillardiere's journal of May 12, 1792, at which date the expedition was in the Buy of Storms, Van Diemen's Land, indicates that even then this sagacious botanist anticipated the great value of this tree for ship-building purposes.
For a long time the Eucalyptus globulus was simply an object of curiosity, and many a botanic garden possessed it without any one knowing of the fact: thus M. Planchon assures us that he saw it in 1854 in the Paris Museum, under the name of E. glauca. In Tasmania the colonists well knew the value of their splendid blue-gum tree, and employed it for a thousand purposes. It became more generally diffused only after the colony of Victoria was founded, an event not yet forty years old. Two names are thenceforth specially connected with the history of the Eucalyptus, viz., those of Baron Ferdinand Müller, of Melbourne, the distinguished botanist, and of M. Ramel. From the Botanic Garden at Melbourne the Eucalyptus crossed the sea to Europe, Africa, and America, like many other plants from the same source which have been acclimated in foreign lands.
Justly, as we think, M. Planchon observes that the term acclimation is apt to suggest erroneous notions, and that it is based upon a profound misconception of the true nature of plants their temperament, so to say. Plants are imported and become naturalized, if you please; but this adaptation in all cases takes place very slowly, gradually, by selection of individuals from successive generations, by the production of races or local varieties which experience shows to be the best fitted to adapt themselves to the special conditions of climate and environment in which they exist. Though there are many grades of naturalization, they can all be reduced to two categories, viz., that of plants which accompany man and domestic animals, and which never separate from them; and, secondly, those plants which, in order
