2 ;o ANATOMY OF THE GYMNOSPERMS 



An Alpine tree rarely 30 m. in height, with a trunk i .50-2. 10 m. in diameter. 

 Wood light, soft, not strong, close grained, satiny, susceptible of a good 

 polish. 



Relative specific gravity 0.4454 



Percentage of ash residue 0.44 



Approximate relative fuel value 44-35 



Coefficient of elasticity in kilograms on millimeters . . 775. 



Ultimate transverse strength in kilograms 307. 



Ultimate resistance to longitudinal crushing in kilograms 6074. 



Resistance to indentation to 1.27 mm. in kilograms . . 1664. 

 (Sargent) 



Dry slopes and ridges near the limits of tree growth, from 2700 feet in 

 British Columbia to 10,000 feet in Colorado. 



Valley of the Fraser River, on Silver Mountain, Yale, and probably much 

 farther north (Macoun); south along the Cascade Mountains and the 

 California Sierras to the headwaters of the San Joaquin River ; east- 

 ward along the high mountains of northern Washington to the Cceur 

 d'Alene and Bitter Root mountains of Idaho, and the divide between 

 Thompson and Little Bitter Root creeks in northern Montana (Sargent). 



5. T. Mertensiana, Carr. 



Western Hemlock 



Transverse. Growth rings thin, the prominent summer wood dense and 

 about equal to the spring wood, from which the transition is gradual. 

 Spring wood very open, the large and thin-walled tracheids conspic- 

 uously squarish, in very regular rows, uniform. Medullary rays very 

 prominent, resinous, rather broad, i cell wide, distant 1-9 rows of 

 tracheids. Resin cells very prominent and resinous, sometimes form- 

 ing short rows of imperfectly organized resin canals on the outer face 

 of the summer wood. 



Radial. Rays uniformly somewhat resinous throughout, the tracheids very 

 unequal, short, sometimes obscure, not infrequently interspersed. 

 Ray cells narrow, conspicuously contracted at the ends, equal to 4-9 

 spring tracheids ; the upper and lower walls medium, unequal, rather 

 strongly pitted ; the terminal walls coarsely pitted ; the lateral walls 

 with small, conspicuously bordered oval pits with an oblong orifice, 

 1-2, rarely 3, per tracheid, becoming obscure in the summer wood. 

 Bordered pits round or elliptical in I row. Pits on the tangential 

 walls of the summer tracheids numerous but small and obscure. 

 Resin canals composed of short, cylindrical resin cells, which unite 

 to form disconnected passages. Resin cells very long and narrow, 

 about 15 fji wide and 150-385 /u, long. 



Tangential. Rays rather numerous, medium to high, resinous, rather 

 broad, the somewhat thick-walled cells rather unequal and variable, 

 round or oval. 



