CONIFERS OF THE ROCKY MOUNTAIN REGION. 23 



drooping and the middle and higher ones trend upward. All of 

 the branches have numerous long, hanging, side branchlets, which 

 are sometimes very long. In dense stands, one-half or two-thirds 

 of the lower branches are shaded out by the time the trees are 10 

 or 15 inches in diameter. Under these conditions the crowns of 

 middle-aged and old trees lose much of their earlier pyramidal form 

 and become rounded or flattened. 



The massive trunks, clear of branches for 80 or 100 feet (in the 

 Pacific region) are straight and taper only slightly. The ashy 

 brown bark of young trees, often with chalky patches, is thin and 

 smooth and but little broken or furrowed, except near the ground, 

 until the trees are from 12 to 14 inches in diameter. Old trees have 

 bark from 5 to 10 inches thick at the base of the trunk, although 

 higher up it is much thinner. Very old trees sometimes have bark 

 from 18 to 24 inches thick. The bark is of a dark brown color 

 outside and a clear red-brown within. It is often very rough, with 

 deep, wide furrows and great ridges, which are connected at in- 

 tervals by narrower diagonally disposed cross ridges. There is 

 great variation in the character and markings of the bark in dry 

 and humid regions, and also on trees in exposed and protected 

 situations. In exposed, dry situations, such as are common in the 

 southern and middle Rockies, trees have rougher and harder bark 

 than in the moist, dense forest of the Pacific region. Moreover, 

 trees of the high, very dry interior Rocky Mountain slopes, par- 

 ticularly young trees, may have soft, corklike, 36 gray-brown bark. 

 This may well be a result of the excessively dry atmosphere, for 

 one or two balsam firs of that region have similar bark. In other 

 characteristics, however, these trees do not differ from those with 

 the ordinary bark. 



Mature foliage is usually a deep yellow-green. In the drier parts 

 of its range, particularly in the Rocky Mountain region, Douglas 

 fir sometimes has blue-grass 37 foliage of varying shades. These 

 blue shades are especially pronounced during the early maturity of 

 the leaves. Each season's growth of leaves remains on the tree 

 about eight years, soon after which it is shed at irregular intervals. 

 The leaves (PL VI) are flat, slightly grooved above and commonly 

 blunt, or very occasionally pointed. 



The cones (Pis. VI, VII) ripen early in August, and by September 

 they are of cinnamon or reddish brown color. Their scales soon 

 begin to open and shed their seed, the cones dropping from the 



36 The variety " Pseudotsuga taxifolia suberosa Engelmann" is a form of Douglas fir with bark of this 

 character. 



37 About 20 or more different garden varieties and other forms of this tree now distinguished in 

 cultivation are based on color of the foliage and similar individual characteristics. 



