ABIKS 263 



to form imperfect resin canals in a more or less continuous zone in 

 the summer wood of distant growth rings. Medullary rays prominent, 

 somewhat resinous, i cell wide, distant 1-8 rows of tracheids. 



Radial. Rays more or less resinous throughout, wholly devoid of tra- 

 cheids. Ray cells chiefly straight, becoming conspicuously fusiform 

 in the summer wood, equal to about 8-u spring tracheids ; the upper 

 and lower walls medium, unequal, more or less strongly pitted through- 

 out ; the terminal walls strongly pitted ; the lateral walls with round 

 or oval, conspicuously bordered pits, the orifice lenticular or oblong, 

 1-2, or in the marginal cells rarely 3-4, per tracheid. Bordered pits 

 in i row, sometimes in pairs, round, the orifice large. Pits on the 

 tangential walls of the summer tracheids minute. Resin cells, when 

 present, short-cylindrical and united to form short resin sacs within 

 the summer wood of distant growth rings. 



Tangential. Rays medium to high, the cells often resinous, chiefly broad 

 but variable from round to oval and oblong, unequal, often in pairs. 



A large tree 61-92 m. high, with a trunk 2.40-3 m. in diameter. 

 Wood light, hard, strong, rather close grained, compact. 



Relative specific gravity 0.4561 



Percentage of ash residue 0.34 



Approximate relative fuel value 45-46 



Coefficient of elasticity in kilograms on millimeters . . 1277. 



Ultimate transverse strength in kilograms 368. 



Ultimate resistance to longitudinal crushing in kilograms 7256. 



Resistance to indentation to 1.27 mm. in kilograms . . 1917. 

 (Sargent) 



Oregon, Cascade Mountains from the Columbia River south to the valley 

 of the upper Rogue River, and along the summits of the Coast Range 

 from the Columbia to the Nestucca River (Sargent). 



10. A. concolor, Lindl. and Gordon 

 White Fir. Balsam Fir 



Transverse. Growth rings broad, the structure rather open throughout. 

 Summer wood prominent, thin, upwards of one third the spring wood, 

 into which it passes very gradually. Spring tracheids medium, squar- 

 ish, thin-walled, and uniform in somewhat regular rows. Resin pas- 

 sages prominent and rather numerous but imperfectly formed, very 

 variable, and often large, forming more or less continuous series 

 within the summer wood, often of distant growth rings. Resin cells 

 few, nonresinous, distant on the outer face of the summer wood and 

 distinguished by (i) the sieve-plate structure of the terminal wall, and 

 (2) their somewhat advanced position. Medullary rays rather promi- 

 nent and somewhat resinous, especially in the summer wood ; i cell 

 wide, distant 2-7, rarely 10, rows of tracheids. 



Radial. Rays somewhat resinous, especially in the summer wood. Ray 

 cells conspicuously contracted at the ends throughout and equal to 



