88 FOREST TREES OP THE PACIFIC SLOPE. 



than 130° F., not uncommonly falling to —60° F. in winter and sometimes above 100° F. 

 during summer. Growing season for tender vegetation is from about four months, in 

 western British Columbia and eastern Alaska, to three weeks on Bering Sea coast. 

 Owing to high latitude, sunlight is less intense during growing season, but of longer daily 

 duration than farther south. In winter, insolation is very weak. 



Tolerance. — Very tolerant of shade, and recovers from suppression up to advanced age. 

 In dense stands it produces heavy crown cover, and frequently shades out tamarack. 

 Most tolerant on wet soils, which it covers with dense stands of slow-growing trees, and 

 least tolerant in dry, well-drained situations, where it grows in more open stands. Re- 

 tains side branches for a long time, producing clear trunks only in very dense stands. 



Reproduction. — Not a prolific seeder, although some seed is usually borne locally each 

 year ; abundant seed production only at rather long, irregular intervals. Seed of moder- 

 ately high germination and with persistent vitality. Germination best on constantly 

 moist mineral and humus soils ; seed germinates well also in forest on decayed fallen 

 trees, moss, and moist decomposed spruce leaf litter. Leaf litter in broadleaf forests 

 not as a rule favorable to germination. Seedlings demand moderate shade for first one 

 or two seasons. 



White Spruce. 

 Picea canadensis (Mill.), B., S., & P. 



DISTINGUISHING CHARACTERISTICS. 



White spruce is considered here because of its range in the interior (at least) 

 of Alaska. It is mainly a tree of the northeastern United States and of Canada, 

 with a very wide distribution in the latter region. In Alaska white spruce 

 varies, according to situation, from a stunted form from 8 to 20 feet high to a 

 well-grown tree from 50 to 75 feet in height and from 12 to 20 inches in diam- 

 eter; much larger trees occur on very favorable sites. Elsewhere it reaches 

 from 80 to 100 feet or more in height, and from 24 to 30 inches in diameter. 

 Trees 3 or 4 feet in diameter and over 100 feet high are rather rare. The trunk 

 is straight, smooth, and clear of branches for one-third to two-thirds of its 

 length, with a somewhat open, irregular, and widely pyramidal crown, the top 

 of which, especially in old trees, may be rounded or flattened ; very often, how- 

 ever, the crowns are sharply pointed. The branches are long and thick, and com- 

 monly curve down and then upward. A striking character of branches is their 

 numerous small, drooping side branchlets. The dense foliage is also character- 

 istic in its light blue-green color, which in some individuals has a distinct 

 whitish tinge. This character has doubtless given the tree its widely recognized 

 common name, "white spruce." Bark of trunks is thin (one-half inch thick) 

 and is early broken into small, thin, pale, ashy-brown scales; the color varies 

 greatly with the density of the stand. The 4-angled leaves (fig. 33) stand out 

 all around the twigs, except at and near their ends, where they are massed on 

 the upper side ; those on the lower side are curved toward the upper ones. 

 Twigs of a season's growth are dark yellow-brown ; as a rule they are smooth, 

 but on the far northwestern forms they are apt to be finely downy. A notable 

 •character of the young shoots and leaves is the fetid, polecat-like odor they 

 emit when bruised ; foliage a year old or older gives off a much less distinct 

 odor. This peculiarity has given the tree its name of " cat spruce." The cones 

 (fig. 33) ripe by the end of the summer, shed their small light clay-yellow-brown 

 seeds (33, a) in September. The pendulous cones are lightly attached and usu- 

 ally fall during autumn or by spring. After shedding their seeds the cones area 

 light clay-brown, whereas just at maturity they may be light grass-green tinged 

 with red or bright rose-red. They vary from about 1 to nearly 2\ inches in 

 length, but they are usually about \\ inches long. When open and dry the cone- 

 scales are so thin and flexible that they can be squeezed together without break- 

 ing them. Seed-leaves, about 6, very slender, and one-half to nearly three- 

 fourths of an inch long. Wood, pale yellowish white, soft, very straight and 



