EVERGREENS OF COLORADO 13 



are so flexible as to enable them to bend readily without breaking. In 

 general it closely resembles the bristle-cone pine, both in its altitudinal 

 range and in habit of growth. It commonly possesses the same bushy 

 form and branching trunk as the foregoing species, although occasional 

 specimens may be found which possess a tall, straight, unbranched trunk. 

 It is much more abundant in this state and reaches a greater size than 

 the bristle-cone pine. The needles of this pine are also borne in bundles 

 of five, but are about one-half longer than those of the bristle-cone pine 

 and instead of remaining on the branchlet for twelve to fifteen years as 

 in that species, in the limber pine they remain only from three to five 

 years. This gives the branches the appearance of being covered with 

 short tufts of needles at the ends of the twigs. 



In this pine the sheath of each bundle of needles is composed of long, 

 thin scales which fall away almost before the foliage has reached full 

 size. Thus in looking at the bundles of needles, the sheath is apparently 

 wanting except during the early part of the season, when the new growth 

 is just coming out. The cones are commonly three to five inches in 

 length, although in some parts of the range of this tree, they are much 

 larger than this. The cone scales are broadly oval and are entirely des- 

 titute of prickles. This feature readily distinguishes the limber pine 

 from the bristle-cone pine. The seeds are about one-third of an inch in 

 length and ordinarily are wingless. 



The bark of young stems and branches is light grey or silvery white. 

 On old trunks it reaches a thickness of one to two inches and is of a 

 blackish brown color. In such cases, it is broken into broad ridges by 

 deep fissures which are often crossed by smaller fissures which separate 

 the ridges into rectangular plates covered by small scales. The wood is 

 rather light, soft, fine grained, with pale yellow sap wood and reddish 

 heart wood. Commercially this tree is of relatively little importance in 

 this state. It is occasionally used in the manufacture of lumber, mine 

 posts, railway ties and for fuel. Occasional specimens may be found which 

 possess straight, unbranched trunks, suitable for posts or for sawn lumber. 



3. ROCK PINE, ROCKY MOUNTAIN YELLOW PINE, BULL PINE 

 Pin us pondcrosa scorpulorum Engelm. 



This is the Rocky Mountain form of Pinus ponderosa, commonly 

 known as bull pine and western yellow pine, a tree which extends from 

 the western Rocky Mountain region to the Pacific slope and from British 

 Columbia to western Texas and Mexico. It is the common pine of the 

 foothills and lower mountain slopes in Eastern Colorado. In some places, 

 for example along the Divide which extends eastward for many miles 

 between Denver and Colorado Springs, this pine reaches well into the 

 plains region. West of the Continental Divide the yellow pine occurs 

 principally in the southwestern quarter of the State, where it reaches its 

 best development as a lumber tree. Among the mountains, the rock pine 

 commonly leaves off at an altitude of about 8,500 feet, although occasional 



