CONIFERS OF THE ROCKY MOUNTAIN REGION. 17 



science. From 1867 to 1898 mountain hemlock was known to most 

 botanists as "Tsuga pattoniana Seneclauze," at the close of which 

 period Prof.' C. S. Sargent showed Tsuga mertensiana to be the 

 correct designation.^^ 



DISTINGUISHING CHARACTERISTICS. 



Mountain hemlock has Uttle general resemblance to the better- 

 known western hemlock. Only its drooping slender branches and its 

 bark suggest hemlock to the casual observer, by whom its fohage 

 might be easily mistaken for that of a spruce or, possibly, of a 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 the exceedingly 

 slender whiplike 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 60 feet high and 

 from 10 to 20 inches in diameter; 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 150 feet high, with a diameter of 30 or 

 40 inches, are sometimes met with. The trunk is often rather sharply 

 tapering. On high steep slopes the trunks have a conspicuous bend 

 at the base in the form of a sled runner. This is produced by heavy 

 snows which annually bend or crush the slender seedlings and saplings 

 to the ground without kiUing them. Later growth fails to straighten 

 entirely the bent stems. The bark is early broken and rough on 

 young trees. That of old trees is about 11 inches thick and of a dull 

 purplish to dark reddish brown color. It is deeply and narrowly 

 furrowed, the rough, hard, distantly connected ridges being 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. Fohage 

 of a season's growth is shed about the fourth year. The blunt- 

 pointed leaves (PI. V) are rounded and plump looking, being unlike 

 the flat, grooved leaves of other hemlocks in this respect, but hke them 

 in having small distinct stems. The leaves clothe the branches aU 

 around, but appear thicker on their upper sides. The main bra,nchlets 

 are unique in having numerous short, erect side twigs; both are 

 minutely downy for several years. 



2' Mountain hemlock is said to have been first introduced into cultivation in Scotland from seeds col- 

 lected by John Jeffrey "on the Mount Baker range of mountains" in 1851 (Murray, Edin. New. Phil. 

 Joum., 289, 1855; Proc. Hort. See. II, 202, 1863). The bluish-leafed form of this tree cultivated for oma^ 

 ment in European gardens has been named "Tsuga pattoniana argentea Beissner" (Handb. Nadelh., 

 410,1891), this name being changed to "Tsuga mertensiana argentea (Beissn.) Sudw." in 1898. Elwes 

 and Henry (The Trees of Great Britain and Ireland, II, 231, 1907) have distinguished a garden form with 

 "greenish foliage" as "Tsuga pattoniana, var. JefEre3ri," stating that it is known only in cultivation. 



49432°— 18— Bull. 680 3 



