278 ANATOMY OF THE GYMNOSPERMS 



Tangential. Rays rather numerous, low to very high. Fusiform rays with 

 a large resin canal without thyloses, the epithelium cells thick-walled. 

 Ordinary rays often very high, chiefly very uniform, and not con- 

 tracted at the position of the rarely interspersed tracheids ; the paren- 

 chyma cells rather unequal, sometimes in pairs, oval or oblong, 

 somewhat variable. 



This species appears to be more or less variable according to local con- 

 ditions of growth. From low elevations specimens appear to exhibit 

 little variation, but from high elevations (Mt. Higgins, Montana, altitude 

 8700 feet) they present very well-defined structural deviations. These 

 appear chiefly in the much narrower and unequal growth rings. 



A tree 30-45 m. high, with a trunk upward of 1.50 m. in diameter. 



Wood heavy, exceedingly hard and strong, rather coarse grained, com- 

 pact, satiny, susceptible of a fine polish, very durable in contact with 

 the soil, and of great economic value. 



Relative specific gravity 0.7407 



Percentage of ash residue 0.09 



Approximate relative fuel value 74- 



Coefficient of elasticity in kilograms on millimeters . . 1658. 



Ultimate transverse strength in kilograms 524. 



Ultimate resistance to longitudinal crushing in kilograms 11,023. 



Resistance to indentation to 1.27 mm. in kilograms . . 2395. 

 (Sargent) 



Abundant in the Kootenai-Columbia valley of British Columbia (Macoun); 

 through the mountain ranges of northern Washington to the western 

 slopes of the Rocky Mountains of Montana; the Blue Mountains of 

 Washington and Oregon ; moist mountain slopes and benches between 

 2500 and 5000 feet elevation ; scattered among other trees, never form- 

 ing separate forests (Sargent). 



2. L. americana, Michx. 



Larch. Black Larch. Tamarack. Hackmatack 



Transverse. Growth rings rather broad and uniform, sometimes double. 

 Summer wood rather dense, about one fourth to one half the spring 

 wood, from which the transition is either gradual or abrupt, the 

 tracheids small, conspicuously unequal and not in very regular rows, 

 distinctly rounded. Spring tracheids large, hexagonal, radially elon- 

 gated, thin. Medullary rays prominent, broad, i cell wide, distant 

 2-8, rarely more, tracheids. Resin passages large, equal to 2-3 

 tracheids, devoid of thyloses ; the epithelium cells flat, rather thin- 

 walled ; the nutritive parenchyma scanty, thick-walled ; not very 

 numerous, chiefly in the summer wood. Resin cells few, widely scat- 

 tering on the outer face of the summer wood, nonresinous, distin- 

 guished by (i) their thinner walls and advanced position, and (2) by 

 the sieve-plate structure of the terminal walls. 



