18 BULLETIN 680, U. S. DEPARTMENT OF AGRICULTURE. 



The cones become full grown in one season. The}" are usually so 

 abundant as almost to cover the branchlets and to bend them down 

 with their weight. When mature the cones are pendulous; very 

 rarely, and then chiefly on stunted trees in exposed situations, are 

 they erect when mature. They vary greatly in length from about 

 one-half an inch to 3 inches; commonly, they are about 2 inches long 

 and three-fourths of an inch thick before opening (PL V). There is 

 great variation in the color of cones at maturity, this ranging from 

 yellowish green to a bluish purple. Different trees of the same forest 

 may each have differently colored mature cones; but the color is a 

 transient characteristic and there is no other difference between such 

 trees. When the cones open, and for some time afterwards, they are 

 of a dull to light brown color, the scales spreading at right angles to 

 the cone axis (PI. V, a) or being strongly bent downward. After the 

 seeds are shed, usually late in September or October, the cones begin 

 falling from the trees, and by spring most of them are down. The 

 pale brown seeds (PL V, b) are provided with large wings which enable 

 the wind to carry them for long distances. Seed-leaves of the 

 mountain hemlock are four in number, and about one-fourth of an 

 inch in length. 



The wood of mountain hemlock is very narrow-ringed, soft, and of a 

 pale reddish brown color. It is without the silvery character peculiar 

 to our eastern hemlock wood. It ranks second in weight among our 

 native hemlocks, a cubic foot of dry wood weighing about 27| pounds. 

 It is practically never used for commercial purposes, and locally only 

 occasionaUy on the prospector's camp fire or for his rough-log cabin. 



OCCURRENCE AND HABITS. 



Tsuga mertensiana grows mainly at timber line, but far north in 

 the Pacific region it occurs at sea level. Southward in the Pacific 

 region and eastward in the Rockies (Map No. 5) its vertical range is 

 determined by the gradual ascent of favorable climatic and moisture 

 conditions, which for these regions confine the tree to high, cold, 

 moist, mountain slopes and valleys. It thrives in most well-drained 

 soils which are not too dry, but best in loose, coarse, moist ones, at 

 elevations ranging from sea level to about 11,000 feet. The highest 

 elevation attained is in the California Sierras. So far as is now 

 known, its vertical range in the Eocky Mountains is between about 

 5,500 and 8,000 feet, or occasionally up to 9,000 feet, 



The best stands occur on flats, gentle slopes, and at the heads of 

 moist valleys, or in sheltered ravines. It has a decided preference 

 for north exposures, doubtless because it encounters less heat and 

 greater soil moisture there. Although often abundant on exposed 

 high slopes, it is usually stunted in such situations, which are least 

 favorable to the best growth. At high altitudes, mountain hemlock 



