334 ANATOMY OF THE GYMNOSPERMS 



the walls rather thin. Resin passages very round, large, somewhat 

 numerous ; the epithelium cells at first flattened and rather thin-walled, 

 quickly passing into large, rounded, thick-walled, and strongly resinous 

 wood-parenchyma cells which often form extensive and somewhat 

 irregular tracts. Medullary rays prominent, resinous, broad, i cell 

 wide, distant 2-10 rows of tracheids. 



Radial. Rays locally and strongly resinous, the resin massive ; the ray 

 tracheids low, marginal, and interspersed, often predominant, strongly 

 dentate and sparingly reticulated in the summer wood. Ray cells of 

 two kinds, but merging and not always clearly distinguishable: (i) 

 thick-walled, fusiform cells ; the terminal walls thin and locally thick- 

 ened ; the upper and lower walls coarsely pitted ; the lateral walls 

 with very variable, oval, or lenticular pits, 2-4, chiefly 3, per tracheid, 

 becoming i in the summer wood ; and (2) thin-walled, fusiform cells ; 

 the terminal, upper, and lower walls thin and not pitted, the former 

 often locally thickened ; the lateral walls with lenticular, chiefly narrow 

 and simple pits, 2-4 per tracheid, becoming 1-2 in the summer wood. 

 Bordered pits in i row, sometimes in pairs, elliptical, becoming smaller 

 toward the summer wood, where they are finally obscure. Pits on the 

 tangential walls of the summer wood wholly wanting. 



Tangential. Fusiform rays rather numerous, low, variable, rather broad 

 and unsymmetrical ; the terminals acute or prolonged ; the cells vari- 

 able, chiefly thick-walled throughout, often resinous. Ordinary rays 

 low, numerous, resinous, and strongly contracted by the frequently 

 interspersed and much narrower tracheids ; the parenchyma cells of 

 two kinds : (i) thick-walled cells chiefly predominant ; and (2) thin- 

 walled cells more or less broken out, interspersed. 



A small tree 18-24 m. high, with a trunk upwards of .45-. 60 m. in diameter. 

 Wood light, soft, strong, brittle, close grained, and compact. 



Specific gravity -5457 



Percentage of ash residue 0.39 



Approximate relative fuel value 54-37 



Coefficient of elasticity in kilograms on millimeters . . 726. 



Ultimate transverse strength in kilograms 355. 



Ultimate resistance to longitudinal crushing in kilograms 5398. 



Resistance to indentation to 1.27 mm. in kilograms . . 2470. 

 (Sargent) 



Dry, rocky ridges and slopes between 5000 and 7000 feet elevation. 

 Arizona, New Mexico, and Chihuahua, Mexico, not common (Sargent). 



31. P. Jeffrey!, A. Murr. 



Bull Fine. Black Pine 



Trans-verse. Growth rings narrow, rather uniform. Summer wood thin 

 and open, or again very thin and very open ; the tracheids uniform in 

 regular rows, more rarely unequal in irregular rows ; the transition from 

 the spring wood rather gradual. Spring tracheids large, hexagonal, 



