FOREST TREES OF THE PACIFIC SLOPE. 95 



Oregon to over 100 Inches in British Columbia and Alaska. Temperature occasionally 

 — .".."i V. on west slope of Rockies in north Idaho, Montana, and British Columbia, 

 and also in parts of Alaska, but elsewhere, especially in coast regions south of 

 Alaska, well above zero. This hemlock generally follows humidity and precipitation 

 of the region. Precipitation and humidity decrease from the coast to the Rockies. 

 Precipitation is much less on east side of coast ranges and Cascades than on the 

 sea slopes ; deficient in interior basins of Oregon, Washington, and British Columbia 

 between Rockies and Cascades; abundant on west slope of Rockies. 



TOLBHANCB. — Wry tolerant of shade throughout life, especially in seedling stages. In 

 later life vertical light necessary tor best growth. Allowed overhead light, it recovers 

 remarkably well from long suppression and renews rate of growth. Prolonged sup- 

 pression in dense shade greatly checks growth. Thrives in .cool, open, humid places 

 with abundant soil moisture. Maintains dense stands, alone, subordinate to others, or 

 as dominating tree with equally tolerant or slow-growing species. 



Reproduction. — Very prolific seeder, reproduces itself freely everywhere under favor- 

 able conditions. Produces some seed every year, but heavy seed years occur at Irregular 

 intervals. Seed with moderate rate of germination and moderately persistent vitality. 

 Germinal ion excellent and growth of seedlings good on wet moss, humus, litter, decaying 

 wood, muck, and mineral soils — the latter less favorable than moist vegetable seed 

 bed. Reproduction abundant under dense shade of mature stands and also in the open 

 on cat-over areas with favorable moist forest floor. Restocks burned over areas at first 

 only sparingly, where light-demanding Douglas fir, pine, larch, fir, etc., come in first. 



Mountain Hemlock; Black Hemlock. 

 Tsuga mertensiana (Bong.) Sargent. 



DISTINGUISHING CHARACTERISTICS. 



Mountain <>r black hemlock, an alpine tree, has little general resemblance to 

 the Better-known western hemlock. Only the drooping slender brandies and 

 its bark suggest hemlock to the casual observer, by whom its foliage might be 

 easily mistaken for that of spruce, or possibly of fir. Forest-grown trees have 

 sharp-pointed, narrowly pyramidal crowns of slender, conspicuously drooping 

 branches ; the upper third of the crown has very short drooping branches, while 

 tbe exceedingly slender whip-like leaders are gracefully pendulous. Trees grown 

 in the open bear branches of the same habit down to the ground, rarely losing 

 them for more than a few feet above ground, even in old age. Ordinarily, 

 mountain hemlock is short, from 25 to GO feet high and from 10 to 20 inches in 

 diameter : the trunk is often rather sharply tapering; on bleak crests, it is only 

 a few feet high or sprawling on the ground. Trees 75 or 80 feet high are not 

 uncommon, while trees 100 or 125 feet high, with a diameter of 30 or 40 inches, 

 are sometimes met with. On high, steep slopes the trunks are strongly bent 

 down the slope at their liases, in the form of a sled-runner. Heavy snows 

 annually bend or crush the slender seedlings and saplings to the ground without 

 killing them and later growth rarely straightens the bent stems. The bark is 

 early broken and rough on young trees. That of old trees is about li inches 

 thick and dull purplish to dark reddish brown. It is deeply and narrowly fur- 

 rowed ; the rough, hard, distantly connected ridges are narrow and rounded. At 

 some distance the trunks have a blue-gray tinge. The dense foliage varies from 

 a dark to a pale blue-green. Foliage of a season's growth is shed about the 

 fourth year. The blunt-pointed leaves (fig. 35) are rounded and plump looking, 

 in this respect unlike the flat leaves of other hemlocks, but like them the Leaves 

 have small distinct steins. They clothe the branches all around, but appear 

 thicker on their upper sides. The main branchlets are unique in having numer- 

 ous short, erect side branches; both are minutely downy for several years. The 

 cones are full grown in one season. They are usually so abundant as to almost 

 cover the branchlets and to bend them down with their weight Usually they 

 are pendulous : very rarely, and chiefly on stunted trees in exposed situations, the 



