314 ANATOMY OF THE GYMNOSPERMS 



contracted by the sparingly interspersed tracheids ; the cells equal, 

 oval, and uniform, thin-walled ; the lateral walls not concave or 

 convex. 



A tree 15-18 m. high, with a trunk upwards of 1.20 m. in diameter. 

 Wood light, soft, close grained, and compact. 



Specific gravity Q-4358 



Percentage of ash residue 0.28 



Approximate relative fuel value 43-42 



Coefficient of elasticity in kilograms on millimeters . . 676. 



Ultimate transverse strength in kilograms 266. 



Ultimate resistance to longitudinal crushing in kilograms 5591. 



Resistance to indentation to 1.27 mm. in kilograms . . 1727. 

 (Sargent) 



Rocky Mountains of British Columbia (Macoun) ; southward through the 

 Rocky Mountains to Utah, Nevada, New Mexico, and Texas; Inyo 

 Mountains and Mount Silliman, California (Sargent). 



10. P. reflexa, Engelm. 

 White Pine 



Transverse. Growth rings variable, often double. Summer wood conspic- 

 uous but thin or upwards of one half the spring wood, from which the 

 transition is gradual, the structure open. Spring tracheids large, squar- 

 ish-hexagonal, the walls rather thickish, conspicuously unequal, and 

 often in irregular rows. Medullary rays not very broad, i cell wide, 

 distant 2-10 rows of tracheids, somewhat prominent ; the side walls of 

 the cells conspicuously inflated and projecting into the adjacent tra- 

 cheid cavities. Resin passages numerous and large, chiefly in or near 

 the summer wood ; the epithelium composed of large and thin-walled, 

 very resinous cells ; when in the summer wood the resin passage is 

 central to a large tract of thin-walled tracheids. 



Radial. Rays nonresinous ; the tracheids numerous, low, marginal, and 

 sparingly interspersed. Parenchyma ray cells straight; the upper and 

 lower walls rather thickish and entire or again somewhat strongly 

 pitted, especially in the summer wood ; the terminal walls thin and 

 entire or locally thickened ; the lateral walls with large, oval, or squar- 

 ish pits which finally become lenticular, 1-2, chiefly i, per tracheid 

 throughout. Bordered pits numerous, elliptical, in i row, distinctly 

 smaller and round toward the summer wood where the orifice becomes 

 a more or less extended slit merging into double striations. Pits on the 

 tangential walls of the summer wood rather small and flat, narrowly 

 lenticular, chiefly confined to the outermost wall where they are rather 

 numerous. Resinous tracheids wanting. 



Tangential. Fusiform rays broad, rather numerous, the cells of the inflated 

 portion very large, thin-walled. Ordinary rays medium to low, not very 

 numerous, nonresinous, rarely contracted by smaller, interspersed tra- 

 cheids ; the parenchyma cells equal, oval, or oblong, the thin side walls 

 strongly inflated, more rarely incurved. 



