The first order of catkin-bearing trees that I shall describe is called Juglandaceæ, and it contains three genera, only two of which, the Walnuts and the Hickories, are common in British gardens. The second order, Salicaceæ, contains also two genera, the Willows and the Poplars; the third, Betulaceæ, contains both the Alders and the Birch trees; the fourth, Corylaceæ or Cupuliferæ, contains the Oak, the Beech, the sweet Chestnut, the Hazel, and the Hornbeam; the fifth, Platanaceæ, is generally considered to include two genera; viz., Platanus and Liquidambar, though this last is, by some botanists, placed in a separate order called Balsamaceæ; and the sixth, Myricaceæ, or the sweet Gale family. All the genera included in these orders, with the exception of those belonging to Juglandaceæ, were formerly comprised in one order, which was called Amentaceæ; from the word Amentum, which signifies a catkin. The seventh and last order I have mentioned in this chapter is called Garryaceæ, and consists of one single genus, Garrya, only lately known in Europe. Of all these orders the largest and most important is Cupuliferæ, as it includes, among other valuable trees, the Oak and the Beech. All the plants mentioned in this chapter have their male and female flowers distinct, many of the genera having them on different plants; and the male flowers are always in catkins, generally long and cylindrical, but sometimes round and ball-shaped. The female flowers are sometimes in catkins also, but sometimes they are produced singly or in pairs. The flowers of both kinds are without petals, or with such as are inconspicuous; and sometimes without even a calyx, but they are always furnished with bracts, which grow so closely to the flower as almost to seem a part of it. The ovaries are generally two-celled, but they rarely remain so, as they become one-celled before the seed is ripe. The style is, in most cases, very short, and the stigma generally two-lobed. The leaves are always alternate, and generally simple, except in the case of the Juglandaceæ. They are all hardy trees and shrubs. JUGLANDACEÆ.—THE WALNUT TRIBE. The genera belonging to this order have compound leaves, and the male flowers in long cylindrical catkins; the male and female flowers being on the same plant. THE GENUS JUGLANS.