PINUS 331 



somewhat thickened, and thus passing into cells of the first order ; 1 1n- 

 lateral walls with oval or lenticular pits, 1-3, chiefly 2, per tracheicl 

 throughout, very unequal and variable in form and size. Bordered 

 pits in i row, sometimes in pairs, elliptical, becoming greatly re- 

 duced in the summer wood, and finally wanting. Pits on the tangential 

 walls of the summer wood wholly wanting. 



Tangential. Fusiform rays rather numerous, medium, narrow ; the acute or 

 rarely prolonged terminals almost wholly composed of tracheids ; the 

 cells of the inflated portion very thin-walled and usually broken out. 

 Ordinary rays rather numerous, low to high, nonresinous and presenting 

 three principal aspects: (i) low rays wholly composed of tracheids 

 and thick-walled parenchyma cells, rarely 2-seriate, at least in part ; 

 (2) i-seriate rays with the thin-walled parenchyma of the central portion 

 much broken out, and showing an interspersed thick-walled paren- 

 chyma cell near the center; and (3) i-seriate rays chiefly composed 

 of thin-walled parenchyma terminated above and below by thick-walled 

 cells and tracheids. 



A tree 24-26 m. high, with a trunk upwards of 1.80 m. in diameter. 

 Wood light, soft, not strong, brittle, and coarse grained. 



Specific gravity 4 I 33 



Percentage of ash residue O-37 



Approximate relative fuel value 41.18 



Coefficient of elasticity in kilograms on millimeters . . 1141. 



Ultimate transverse strength in kilograms 325. 



Ultimate resistance to longitudinal crushing in kilograms 5874. 



Resistance to indentation to 1.27 mm. in kilograms . . 1475. 

 (Sargent) 



The Coast Range of California, most abundant and attaining its greatest 

 development in the San Jacinto Mountains (Sargent). 



28. P. tuberculata, Gord. 



Knob-Cone Pine 



Transverse. Growth rings thick. Summer wood prominent, open, upwards 

 of equal to the spring wood ; the tracheids very unequal in regular 

 rows, distinctly rounded, or the outermost more or less compressed 

 and with much thinner walls; the transition from the spring wood 

 gradual. Spring tracheids hexagonal, somewhat variable, in regular 

 rows, the walls thin. Resin passages rather numerous, chiefly in the 

 summer wood, scattering, large ; the epithelium in 1-3 rows of large 

 and very thin-walled and resinous cells which form a more or less 

 extended tract and often merge into thicker-walled parenchyma or thin- 

 walled tracheids. Medullary rays rather broad, i cell wide, not prom- 

 inent, sparingly and locally resinous, distant 2-15 rows of tracheids. 



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

 tracheids about equal to the parenchyma cells, sometimes predominant 

 and interspersed, the upper and lower walls dentate, more or less 

 reticulated throughout. Ray cells of two kinds: (i) thick-walled, 



