PINUS 3 1 9 



15. P. rigida, Mill. 



Pitch Pine 



Transverse. Growth rings thick. Summer wood dense, sometimes rather 

 open, very prominent, often double, the transition from the spring wood 

 gradual or somewhat abrupt ; the tracheids rounded, not uniform, in 

 rather irregular rows. Spring tracheids large, squarish-hexagonal, very 

 unequal in regular rows. Resin passages large and numerous, chiefly 

 in the summer wood; the epithelium in 1-2 rows of large, irregularly 

 rounded, thin-walled, and often resinous cells which sometimes become 

 thicker-walled in the outer limits, forming more or less extensive tracts 

 eccentrically developed about the canal. Medullary rays rather promi- 

 nent but few, distant 2-16, rarely 27, rows of tracheids. This wood 

 shows a strong tendency to radial fracture. 



Radial. Rays nonresinous ; the tracheids strongly reticulated throughout, 

 sparingly interspersed, very low, not conspicuously predominant. Ray 

 cells of one kind, rarely of two kinds, chiefly low and long fusiform ; the 

 terminal, upper, and lower walls very thin and usually much broken 

 out; the lateral walls with very variable, lenticular, or oval pits: (l) 

 upwards of 6 per tracheid ; and (2) 1-3, chiefly 2, per tracheid, usually 

 becoming more prominent in the low rays, and in the summer wood 

 often distinctly bordered, or again simple and very variable, often large. 

 Bordered pits in I row or pairs, elliptical. Pits on the tangential walls 

 of the summer wood wholly wanting. 



Tangential. Fusiform rays not very numerous, rather low and broad ; the 

 terminals acute and composed of a few small tracheids ; the cells of the 

 inflated portion very thin-walled and large, but usually much broken out. 

 Ordinary rays chiefly rather low and presenting two principal aspects: 

 (i) low rays composed of thin-walled parenchyma much broken out, 

 and a few small, terminal tracheids ; and (2) higher rays of similar 

 parenchyma cells with small, terminal, and few interspersed tracheids, 

 the latter causing local contractions. 



A tree 12-24 m - high* with a trunk upwards of .90 m. in diameter. 

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



Specific gravity 0.5151 



Percentage of ash residue 0.23 



Approximate relative fuel value 5 l -39 



Coefficient of elasticity in kilograms on millimeters . . . 581. 



Ultimate transverse strength in kilograms 316. 



Ultimate resistance to longitudinal crushing in kilograms . 5687. 



Resistance to indentation to 1.27 mm. in kilograms . . . 2123. 

 (Sargent) 



Valley of the St. John River, New Brunswick, to the northern shores of 

 Lake Ontario (Macoun) ; south through the Atlantic states to Georgia ; 

 westward to the western slopes of the Allegheny Mountains of West 

 Virginia and Kentucky (Sargent). 



