The leaves are flat and slender, not in bundles, as in the Scots Pine, but arranged along the branchlets in two or three dense ranks. They are dark, rich green above, about an inch long, and on the flattened underside there is a bluish-white stripe on each side of the midrib, which gives a silvery appearance to the foliage when upturned, as is usual on the fertile branches. These leaves endure from six to nine years. The flowers appear in May at the tips of the branches. The male flowers are about three-quarters of an inch long, and consist of two or three series of overlapping scales, enclosing the yellow stamens. The cones are cylindrical, with a blunt top, always erect, 6 to 8 inches long, and from 1-1/4 to 2 inches in diameter. On the back of each of the broad scales there is a long, slender, pointed bract, which extends beyond the scale and turns downward. At first these cones are green, then become reddish, and when mature are brown; but maturity is not reached until eighteen months after their appearance. The angular seeds are furnished with a broad wing twice their length. They are shed by the cones in the spring following their maturity, the scales falling at the same time and leaving the core of the cone on the tree. As a rule, the tree does not produce fertile seeds until it is about forty years of age, but seedless cones are formed from its twentieth year. Although the flowers of both sexes are found on the same tree, it may be that for a series of years only cones are produced. Until the Silver Fir is about twelve years old its growth is slow, and its annual increase is only a few inches, but later it will be as many feet. During this early stage spring frosts often destroy the leader-shoot, but its place is taken by another shoot; and soon the symmetry of the tree is restored. If this occurs at a later stage, however, the tree bears evidence of it in a forked trunk. It is a deep-rooting species, with a branching tap-root, and succeeds best in an open soil that is moist without being wet. [Illustration: _Pl. 158._ Bole of Silver Fir.] The timber, which has an irregular grain, is strong, and does not warp; but it is soft, and not enduring where it is exposed to the weather. It is yellowish-white in colour, and is largely used for all interior work. * * * * * [Illustration: _Pl. 159._ Spruce Firs.] [Illustration: _Pl. 160._ Bole of Spruce Fir.] The Spruce Fir (_Picea excelsa_).