ARBORETUM.

ABIES-THE SPRUCE FIR.

THE species comprised in this genus were formerly arranged in that of Pinus; but they have been separated on account of the different habits of growth and the disposition of their leaves. The Abies contains such species as have short, solitary, needleshaped, angular leaves, such as the Spruces and Silver Fir; while those of Pinus have from two to five leaves growing together, surrounded by a sheath at the base. The scales of the cones in the Abies tribe are also much thinner and flatter than those of the Pinus. N. O. Coniferæ. L. S. Monæcia Monadelphia.

For other Coniferæ, see Araucaria, Cedrus, Cupressus, Ephedra, Juniperus, Larix, Pinus, Salisburia, Taxodium, Taxus, and Thuja.

ACACIA-THE ACACIA.

The Egyptian thorn, or binding bean-tree, was called by the Greeks akakia, from akazo, to sharpen-hence the Latin name acacia. When the American locust, or false acacia, was first introduced into Europe, it was supposed to be a species of the acacia known to the ancients, on account of its thorny branches and winged leaves bearing a resemblance to it. It was, however, ascertained, that it did not belong to the