310 ANATOMY OF THE GYMNOSPERMS 



numerous, nonresinous, low to medium, slightly contracted by the 

 occasionally interspersed tracheids. Parenchyma ray cells not very 

 thick-walled, equal, rather uniform and oval, more rarely becoming 

 either round, oval, or oblong; sometimes with interspersed thin-walled 

 cells of similar form and size. 



A tree 15-30 m. high, with a trunk upwards of 2.40 m. in diameter. 

 Wood light, soft, not strong, very close grained, and compact. 



Specific gravity 0.5572 



Percentage of ash residue 0.30 



Approximate relative fuel value 55-56 



Coefficient of elasticity in kilograms on millimeters . . 715. 



Ultimate transverse strength in kilograms 279. 



Ultimate resistance to longitudinal crushing in kilograms 5209. 



Resistance to indentation to 1.27 mm. in kilograms . . 2140. 

 (Sargent) 



Dry, gravelly ridges ; mountains of southeastern California, Nevada, north- 

 ern Arizona, and southern Utah to Colorado above 7500 feet, in Colorado 

 reaching 12,000 feet (Sargent). 



6. P. edulis, Engelm. 

 Pinon. Nut Pine 



Transverse. Growth rings narrow, unequal. Summer wood thin, of 3-4 

 tracheids, and not prominent, but very open throughout ; the tracheids 

 strongly unequal in conspicuously irregular rows, the walls thin, the 

 transition to the spring wood gradual. Spring tracheids open, squarish, 

 unequal, and in more or less irregular rows, the walls thin. Medullary 

 rays not very prominent, numerous, rather broad, i cell wide, dis- 

 tant 2-7 rows of tracheids. Resin passages numerous, large, the 

 many-layered epithelium often forming extensive tracts composed 

 of large and very variable, often thick-walled, somewhat resinous 

 cells. 



Radial. Rays very sparingly resinous ; the tracheids marginal, rarely inter- 

 spersed. Parenchyma ray cells conspicuously narrower at the ends, 

 short, of 2 kinds: (i) the upper and lower walls thick and entire or 

 distantly pitted, becoming more strongly pitted locally or in the sum- 

 mer wood ; the terminal walls generally thick and coarsely pitted or 

 rarely thin and devoid of pits ; the lateral walls with small and round 

 pits with a variable, often obscure border and a lenticular orifice, 1-4, 

 more rarely 5 or 6, in the marginal cells, in the summer wood becoming 

 2, per tracheid ; and (2) thin-walled cells sparingly interspersed and 

 conterminous with those of the first kind ; the terminal walls thin and 

 locally thickened ; the upper and lower as well as the lateral walls 

 devoid of pits. Bordered pits numerous, small, elliptical, in i row. 

 Pits on the tangential walls of the summer tracheids numerous on the 

 outermost wall, becoming fewer in the older tracheids, rather small 

 and broadly lenticular. Resinous tracheids wanting. 



