PINE TREES OF ROCKY MOUNTAIN REGION". 31 



The foliage, borne in heavy brush-like clusters at the ends of bare 

 branches, is a deep yellow-green. The leaves (Pis. XVIII, XIX) 

 occur in bundles of 3 (sometimes of 2 and rarely of 4 and 5, and then 

 chiefly on saplings). They vary in length from about 4f to 11£ 

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

 three years. The edges of the leaves have minute teeth (serratures). 

 A cross section of the leaves shows from 2 to 5 resin ducts, the usual 

 number being 2. 



The cones (Pis. XVIII, XIX) mature early in August of the 

 second season and shed their seeds mainly during September. The 

 cones of some trees are a bright grass green when mature, while those 

 of other trees are a dark purple, there being no other essential differ- 

 ence between trees bearing cones so dissimilar in color. Cones vary 

 in length from 2f to about 5| inches and in width from If to about 

 2 inches. The ends of the cone scales are russet-brown and shiny. 

 After the seeds are shed, the cones begin to fall, and by early winter 

 they are all down. A notable characteristic of the cones of this pine 

 is that when they break away from the branch some of the basal 

 scales are left on the tree. The seeds (PI. XVIII, a), which vary 

 greatly in size, are marked with purple spots and blotches on a dull 

 yellowish ground, while the wings are a light purple-brown. The 

 number of seed-leaves varies from 5 to 9 (PL XVIII, b). 



Western yellow pine wood is narrow-ringed, the rather thick layer 

 of sapwood being nearly white and the heartwood ranging from a 

 pale lemon-yellow to an orange-brown or a reddish yellow. It varies 

 greatly in texture according to the age of the tree. Young trees have 

 moderately hard, resinous, strong wood; the wood of old trees is 

 brittle, only slightly resinous, and very soft — so much so that lumber 

 cut from such trees is sold as " white pine." In general a cubic foot 

 of dry wood weighs from about 28| to 29f pounds. The weight of 

 wood from very old, slowly grown trees would probably not exceed 

 about 25 pounds per cubic foot. It is one of the most valuable com- 

 mercial woods produced in the Rocky Mountain region, being used 

 for all sorts of dimension timber under cover, for interior and ex- 

 terior work, railroad ties, mining timber, fuel, etc. It is, however, 

 only moderately durable in contact with earth or when exposed to 

 the weather in an unprotected state. 



OCCTJBKENCE AND HABITS. 



Western yellow pine occurs on dry and moist slopes, on the tops of 

 ridges and in canyon bottoms, in general at elevations between 

 1,800 feet (Pacific region) and 10,300 feet (southern Rockies), the 

 main forest growth in the Rocky Mountain region being found be- 



