BULLETIN 680, U. S. DEPARTMENT OF AGRICULTURE. 



DISTINGUISHING CHARACTERISTICS. 



The largest tamarack trees in the Rocky Mountain region are 

 seldom over 50 feet high and 12 or 14 inches in diameter. Tamarack 

 has a single straight, slightly tapering trunk, and a narrow, sharply 

 conical crown of slender, horizontal branches, which, during the 

 first 25 or 30 years, extend nearly down to the ground. Later the 

 trunks are clear of branches for one-half or two-thirds of their length. 

 The thin, scaly bark is reddish brown, but outwardly more or less 

 weathered to an ashy brown. Twigs of a season's growth are smooth 

 and whitish at first, but by winter they become a dull yellowish 

 brown. 



Mature leaves (the juvenile form is scattered singly on vigorous 

 leading shoots) occur in clusters of about 12 to 20 (PI. I), and are 

 indistinctly triangular in cross section (convex on the top side, with 

 a ridge beneath) and from about seven-eighths of an inch to 1J 

 inches long. In cross section the leaf shows two minute resin ducts 

 close to its edges. 



The cones (PI. I), matured in early autumn of one season, are pale 

 russet-brown, as are the minute- winged seeds (PI. I,/), which escape 

 slowly from the gradually opened cone scales during late autumn 

 or early winter; the upright position of the cones doubtless prevents 

 the seeds from escaping as rapidly as do the seeds from the pendent 

 cones of other conifers. 



Wood of the tamarack is a pale yellowish brown, and varies in 

 texture from narrow-ringed to moderately wide-ringed, according 

 as the trees are grown in dense or open stands. It is rather hard 

 and heavy, durable, elastic, and fairly straight-grained, 11 a cubic 

 foot of dry wood weighing nearly 39 pounds. Large trees have a 

 rather thin layer of whitish sap wood, which is much thicker in young 

 trees. The wood is used chiefly for telegraph and telephone poles 

 and for railroad ties, the largest trees being cut for rough lumber. 



OCCURRENCE AND HABITS. 



Tamarack enters the Rocky Mountain region (Map No. 1) only 

 north of the Canadian boundary, and occurs mainly on the east 

 side of the Canadian Rockies. It is most abundant in sphagnum 

 swamps and muskegs; but the largest trees occur on the better- 

 drained margins of swamps and lakes, moist, porous benches, and 

 bottom lands. It thrives also on moist, well-drained deep-soiled 

 hillsides. In the Rocky Mountain region the tamarack grows at 

 elevations between about 600 and 1,700 feet; its vertical distribution 

 elsewhere in its range is, however, imperfectly known at present. 



11 01dtreesoftenhaveanouterlayer,3to 4 inches thick, spirally twisted, within which the earlier formed 

 trunk wood is straight-grained. 



