PINACEAE 



Mountain Hemlock. Black Hemlock 

 Tsuga mertensiana (Bong.) Carr. 



HABIT. An alpine tree 75-100 feet high and 2 1/2 -3 J/2 feet 

 in diameter; trunk tapering and long clear, or knotty and mal- 

 formed; crown open, pyramidal, with slender, drooping branches 

 and drooping terminal leader; a sprawling shrub at timber line. 



LEAVES. Semicircular in cross section; Vi-l inch long; pale 

 bluish-green and stomatiferous on all surfaces; upper surface 

 often keeled or grooved; abruptly narrowed into straight or 

 twisted petiole; extending from all sides of twig or crowded 

 toward upper side; bluntly pointed. 



FLOWERS. Male purple on slender drooping stems; female 

 purple or green, slender-tipped bracts longer than scales. 



FRUIT. Vz-'iVi inches long, (mostly 2 inches); oblong- 

 cylindric; yellow-green to purple; scales oblong-obovate and 

 spreading at right angles or reflexed when mature. Seed: Y^ 

 inch long; H as long as wing. 



TWIGS. Thin or stout; dense, short, pale, pubescence for 

 2-3 years; light red-brown, becoming gray-brown and scaly. 

 Winter buds: conical, Vs inch long, acute, red-brown, outer 

 scales with awl-like tip. 



BARK. Rather thin on large trees (1-1 V2 inches), early 

 broken and rough on young trees; on old trunks hard, purplish 

 to red-brown, with deep, narrow furrows separating narrow, 

 rounded ridges; contains large quantities of tannin. 



WOOD. Little used and inferior in quality to western hem- 

 lock; light, soft, not strong, and close-grained. 



SILVICAL CHARACTERS. Tolerant; growth slow; trees 

 over 500 years of age seldom found; reproduction generally 

 abundant; shallow, wide-spreading root system. 



HABITAT. Hudsonian and Canadian zones; altitudinal 

 range from sea level (Alaska) to 1 1 ,000 feet, but mostly near 

 timber line; at its best on cool, moist, deep soils of northern 

 exposure, moisture being essential; in pure stands or in mix- 

 ture with alpine fir, alpine larch, Engelmann spruce, white- 

 bark, lodgepole, and western white pines. 



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