PINUS 335 



very unequal in regular rows, the walls rather thin. Resin passages 

 large, scattering ; the epithelium composed of very large, rounded, 

 rather thin-walled and variable cells in 1-3 rows, often forming rather 

 large tracts. Medullary rays broad, i cell wide, not very prominent, 

 distant 2-16 rows of tracheids. 



Radial. Rays nonresinous ; the tracheids strongly dentate and more or less 

 reticulated throughout, numerous and strongly predominant. Ray 

 cells of two kinds: (i) thick-walled cells prominent, fusiform, equal 

 to about 5 spring tracheids ; the terminal walls locally thickened ; the 

 upper and lower walls strongly thickened and pitted ; the lateral walls 

 with prominent, round pits, 2-5, chiefly 3-4, per tracheid, conter- 

 minous with and merging into the cells of the second order; and 

 (2) fusiform cells equal to about 5 spring tracheids ; the terminal 

 walls thin and not locally thickened ; the upper and lower walls thin 

 and entire or more rarely locally thickened ; the lateral walls with 

 lenticular or oval, very variable pits, 1-4 per tracheid. Bordered pits 

 in i row, sometimes in pairs, elliptical, becoming quickly reduced in 

 the summer wood, and finally 7.2 /A. Pits on the tangential walls of 

 the summer wood wholly wanting. 



Tangential. Fusiform rays few, medium, the terminals acute or somewhat 

 prolonged ; the cells of the inflated portion large and thin-walled, 

 usually much broken out. Ordinary rays rather numerous, medium to 

 high, nonresinous, chiefly composed of narrow tracheids with inter- 

 spersed and much broader parenchyma cells. Parenchyma cells of two 

 kinds : (i) thick-walled cells which predominate in low rays, becoming 

 interspersed in high rays ; and (2) the usually broader, more squarish, 

 and thin-walled cells. 



A large tree 30-31 m. high, with a trunk upwards of 4 m. in diameter. 

 Wood light, strong, hard, rather coarse grained, and compact. 



Specific gravity 0.5206 



Percentage of ash residue 0.26 



Approximate relative fuel value 5-53 



Coefficient of elasticity in kilograms on millimeters . . . 925. 



Ultimate transverse strength in kilograms 318. 



Ultimate resistance to longitudinal crushing in kilograms 6679. 



Resistance to indentation to 1.27 mm. in kilograms . . . 1850. 

 (Sargent) 



Dry, gravelly slopes between 6000 and 8000 feet elevation. Along the 

 Sierra Nevadas of California from Siskiyou Mountains to the San Ber- 

 nardino and San Jacinto mountains (Sargent). 



32. P. ponderosa, Lawson 

 Yellow Pine. Bull Pine 



Transverse. Growth rings thin, variable. Summer wood variable, dense, 

 sometimes open, the transition from the spring wood often abrupt ; the 

 tracheids round-hexagonal, unequal, and in somewhat irregular rows. 



