Each leaf is flat and slender, and on the upper side it is a dark glossy green; the edges are rolled back on to the under-side of the leaf, which is much paler in colour. The centre rib of the leaf is much raised, and looks like a slender cord, and on each side of this cord, between it and the curled-back leaf edge, there runs a silvery white line; it is from this silvery line that the tree gets its name. Notice that the leaf twigs of the Silver Fir do not droop in the feathery way they do in the Spruce; they are much stiffer, and stand out all round the branch; also, there is not nearly such a marked upward curve at the tip of the branch as you find in the Spruce Fir. The leaves of the Silver Fir remain on the tree eight or nine years, but each year the tree lengthens its sprays, and the young leaves are a beautiful pale yellowish green colour, almost as pale as the young leaves of the primrose. The stamen flowers (3) grow at the ends of the young sprays. They consist of a few overlapping scales with a cluster of stamens inside. The seed flowers or cones (4) grow on the same tree, sometimes on the same branch, and they become cones in the same way as the seed flowers of the Pine and the Spruce. But you will at once notice a difference. The cones of the Silver Fir grow upright; they sit on the branches with their tops looking up to the sky, whereas the cones of the Spruce and the Scotch Pine when full grown hang down from the ends of the spray with their tips pointing to the ground. If there are any cones visible you will never mistake the Silver Fir for the Spruce. The ripe cones (5) are made up of many thin, soft scales which overlap each other closely, and each scale ends in a sharp point which turns backward; this gives the cone a hairy appearance. At first the cones are green, like those of the Scotch Pine, but soon they turn purple, and when quite ripe they are a rich red-brown. If the tree is old enough--that means if it is forty years of age--you will find small angular seeds (6), with a long filmy wing attached, nestling behind each scale. But if the tree is still young, the cones are seedless. It takes eighteen months for the cone to ripen, and when the seeds are ready and they and the red-brown scales fall from the cone, a bare brown stick is left standing upright on the branch. The wood of the Silver Fir is very valuable, and it is used for many purposes; doors and window-frames and floors are constantly made of it, and for ship-building it is in great demand. In Switzerland there are great forests of Silver Fir, but they grow high on the mountain sides, where there are no roads and no means of getting the trees brought down after they are felled. But at Lucerne, a town on the shores of a large lake, with great forests on the mountains above, the people invented an excellent way of overcoming this difficulty.