344 ANATOMY OF THE GVMNOSPERMS 



40. P. palustris, Miller 

 Long -Leaved Pine. Southern Pine. Yellow Pine 



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

 very thin, the transition from the spring wood very abrupt ; the tracheids 

 very uniform in regular rows. Spring tracheids squarish, rather uniform, 

 in regular rows, often radially elongated, the walls rather thick. Resin 

 passages numerous and large, chiefly in the summer wood; the epithe- 

 lium composed of large, rounded, often resinous cells in i row, fre- 

 quently becoming several-rowed in part and forming more or less 

 extensive and strongly eccentric tracts about the canal. Medullary rays 

 very prominent, broad, i cell wide, distant 2-10, more rarely 15, rows 

 of tracheids. 



Radial. Rays sparingly resinous throughout ; the ray tracheids often inter- 

 spersed, commonly predominant, very strongly reticulated throughout. 

 Ray cells of two kinds : (i) rather few but prominent and conterminous 

 with tracheids into which they merge ; the terminal walls thin and not 

 pitted ; the upper and lower walls somewhat strongly but unequally 

 thickened and pitted ; the lateral walls with broadly and variously len- 

 ticular or round pits, 2-5 per tracheid ; and (2) very long-fusiform cells ; 

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

 out ; the lateral walls with very variable, lenticular, or oval, sometimes 

 very large, pits, 2-6, chiefly about 4, per tracheid, in the summer wood 

 reduced to i. Bordered pits conspicuously in 1-2 rows, elliptical. Pits 

 on the tangential walls of the summer wood wholly wanting. 



Tangential. Fusiform rays not numerous, often very high, acute, the linear 

 terminals much prolonged with terminal or interspersed tracheids, but 

 with the structure very commonly wanting except at the extremities ; 

 the low, inflated portion usually showing only a remnant of very thin- 

 walled, delicate tissue. Ordinary rays medium, rather numerous, broad, 

 presenting three principal aspects: (i) low rays with few, thin-walled 

 parenchyma cells much broken out, and terminal tracheids of very vari- 

 able size ; (2) higher rays of several large, thin-walled parenchyma cells 

 much broken out, and narrow, oval to oblong, terminal tracheids, rarely 

 with interspersed thick-walled parenchyma ; and (3) the highest rays 

 composed of a few large, thin-walled parenchyma cells, with small, ter- 

 minal, and narrow, often high and interspersed tracheids. 



A tree of the greatest economic value 18-29 m - l"gh> w i tn a trunk upwards 



of i. 20 m. in diameter. 

 Wood heavy, exceedingly hard, very strong and tough, coarse grained, com- 



pact, and durable. 



Specific gravity .............. 0.6999 



Percentage of ash residue ........... 0.25 



Approximate relative fuel value ......... 69.82 



Coefficient of elasticity in kilograms on millimeters . . . 1,488. 



Ultimate transverse strength in kilograms ...... 490. 



Ultimate resistance to longitudinal crushing in kilograms 10,074. 



Resistance to indentation to 1.27 mm. in kilograms . . . 2,508. 

 (Sargent ) 



