PIN US 339 



walls thin and locally thickened ; the upper and lower walls more or 

 less thickened and coarsely pitted ; the lateral walls with lenticular 

 or oval, variable pits, 2-6, chiefly 4, per tracheid, finally becoming slit- 

 like and reduced to i in the summer wood or eventually obsolete, often 

 conterminous with tracheids or with thin-walled parenchyma cells ; and 

 (2) the predominant elements ; the terminal, upper, and lower walls thin ; 

 the lateral walls with very variable, oval, or lenticular pits, 1-4 or more 

 rarely 5, chiefly 4, per tracheid, in the summer wood merging into pro- 

 longed slits or finally into round, bordered pits with an oblong, narrow 

 orifice; fusiform, chiefly high. Bordered pits in I row or pairs, ellip- 

 tical, becoming round and conspicuously smaller toward the summer 

 wood, where they are finally reduced to 7.2 /JL. Pits on the tangential 

 walls of the summer wood wholly wanting. 



Tangential. Fusiform rays medium, rather few, narrow ; the terminals acute 

 and composed of large and small tracheids ; the inflated portion com- 

 posed of thin-walled tissue, much broken out and more or less resinous. 

 Ordinary rays chiefly low and presenting three principal aspects: (i) 

 low rays distinctly fusiform, with a large tracheid in the center and 

 small terminal tracheids ; (2) higher rays of i-several large, thin-walled, 

 and resinous cells, much broken out, with or without interspersed thick- 

 walled cells, sometimes in pairs, and terminal tracheids of variable 

 size ; and (3) the highest rays composed of large, thin-walled paren- 

 chyma cells, often with resin, but usually much broken out, terminal 

 tracheids and i -several small, interspersed tracheids, causing local 

 contractions. 



A tree 24-36 m. high, with a trunk upwards of .90 m. in diameter. 



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



Specific gravity -539 



Percentage of ash residue 0.30 



Approximate relative fuel value 5 2 -93 



Coefficient of elasticity in kilograms on millimeters . . . 543. 



Ultimate transverse strength in kilograms 281. 



Ultimate resistance to longitudinal crushing in kilograms 5765. 



Resistance to indentation to 1.27 mm. in kilograms . . . 2496. 

 (Sargent) 



Sandy, generally barren soil. Long and Staten islands, New York ; south- 

 ward usually near the coast to South Carolina and westward through 

 eastern and middle Kentucky to southeastern Indiana (Sargent). 



36. P. muricata, D. Don 



Prickle -Cone Pine 



Transverse. Growth rings thick. Summer wood prominent but rather thin, 

 about one fifth the spring wood, variable, both dense and open ; the 

 tracheids variable, in the open zones often much compressed and in 

 irregular rows, the walls variable ; the transition from the spring wood 

 rather gradual. Spring tracheids ^hexagonal, unequal, in regular rows. 



