Farther south, in central Bosnia, the oak rarely mounts beyond the foothills, being superseded by the beech, elm, ash, fir and pine, up to 5000 ft.
In places suited to its growth it seems to flourish nearly as well as in the woods of Norway or Switzerland; but as it needs for its successful cultivation as a timber tree soils that might be turned to agricultural account, it is not so well adapted for economic planting in Britain as the Scotch fir or larch, which come to perfection in more bleak and elevated regions, and on comparatively barren ground, though it may perhaps be grown to advantage on some moist hill-sides and mountain hollows.
The guides or conductors in the pit may be constructed of wood, in which case rectangular fir beams, about 3 by 4 in., are used, attached at intervals of a few feet to buntons or cross-beams built into the lining of the pit.
Spruce Fir (Picea excelsa B, Cone and foliage.
The quantity obtained from each fir is very variable, depending on the vigour of the tree, and greatly lessens after it has been subjected to the operation for some years.
Others have hollow or funnel-shaped ends and are constricted at the middle like a dice cup. In some rocks small rod-like microlites are grouped together in a regular way to form growths which resemble fir branches, fern leaves, brushes or networks, in the same manner as minute needles of ice produce star-like snow crystals or the frost growths on a window pane.
White fir is found above the foot hill zone, and heavy growths of cottonwood along the streams in the Bighorn region.
From the coast to the eastern base of the Cascade Mountains the state is heavily timbered, except in small prairies and clearings in the Willamette and other valleys, and the most important tree is the great Douglas fir, pine or spruce (Pseudotsuga Douglasii), commonly called Oregon pine, which sometimes grows to a height of 300 ft., and which was formerly in great demand for masts and spars of sailing-vessels and for bridge timbers; the Douglas fir grows more commercial timber to the acre than any other American variety, and constitutes about five-sevenths of the total stand of the state.
Nowhere more abundant than in the Scandinavian peninsula, this tree is the true fir (fur, fura) of the old Norsemen, and still retains the name among their descendants in Britain, though botanically now classed as a pine.
Introduced into Britain at the beginning of the 17th century, the silver fir has become common there as a planted tree, though, like the Norway spruce, it rarely comes up from seed scattered naturally.