336 ANATOMY OF THE GYMNOSPERMS 



Spring tracheids squarish-hexagonal, variable, in somewhat regular rows, 

 rather thick-walled. Resin passages medium, numerous, chiefly in the 

 summer wood; the epithelium in 1-3 rows of rather large and very 

 thin-walled cells, succeeded by thick-walled elements, the whole forming 

 a somewhat extended tract which commonly breaks out in making trans- 

 verse sections. Medullary rays very broad, i cell wide, nonresinous, 

 not numerous, distant 2-15, or sometimes 20 rows of tracheids. 



Radial. Rays nonresinous ; the tracheids predominant or equal to the paren- 

 chyma cells, and usually strongly reticulated. Parenchyma cells of two 

 kinds : ( i ) rather few ; the terminal walls thin and locally thickened ; 

 the upper and lower walls rather thick but not very strongly pitted ; 

 the lateral walls with very conspicuous, round or lenticular, very vari- 

 able pits, 2-4, rarely 5, per tracheid ; and (2) variously contracted cells, 

 the terminal, upper, and lower walls thin and entire ; the lateral walls 

 with lenticular or oval pits, 1-4 per tracheid. Bordered pits in I row, 

 round or more generally elliptical. Pits on the tangential walls of the 

 summer wood wholly wanting. 



Tangential. Fusiform rays somewhat numerous, low to medium ; the termi- 

 nals acute, composed wholly of tracheids ; the cells of the inflated por- 

 tion very thin-walled and usually broken out. Ordinary rays low, 

 numerous, nonresinous; the tracheids chiefly terminal or when inter- 

 spersed causing a slight contraction ; the thick-walled parenchyma cells 

 chiefly terminal, few, the thin-walled parenchyma occupying the central 

 region and forming the greater portion of the ray, generally broken out, 

 the cells oval, variable. 



A large tree 61-91 m. in height, with a trunk upwards of 4.57 m. in 



diameter. 

 Wood varying greatly in quality and value, heavy, hard, strong, brittle, not 



coarse grained or durable, compact. 



Specific gravity 0.4715 



Percentage of ash residue 0.35 



Approximate relative fuel value 46.99 



Coefficient of elasticity in kilograms on millimeters . . . 887. 



Ultimate transverse strength in kilograms 307. 



Ultimate resistance to longitudinal crushing in kilograms 6037. 



Resistance to indentation to 1.27 mm. in kilograms . . . 1719. 

 (Sargent) 



Interior of British Columbia south of latitude 51, south and east along the 

 mountains of the Pacific region to Mexico, the Black Hills of Dakota, 

 Colorado, and western Texas. Dry, rocky ridges; rarely in cold, wet 

 swamps, reaching its greatest development on the western slope of the 

 California Sierras. After Pseudotsuga Douglasii, the most generally dis- 

 tributed and most valuable timber tree of the Pacific forests (Sargent). 

 The distribution of this species and the qualities of the wood are not 

 clearly separable from the next species. 



