324 ANATOMY OF THE GYMNOSPERMS 



South Carolina to the Chattahoochee region of Florida, chiefly near the 

 coast, thence through the Gulf States south to latitude 32 30' to the 

 valley of the Pearl River, Louisiana, its greatest development being in 

 Alabama and Mississippi (Sargent). 



20. P. echinata, Mill. 

 Yellow Pine. Short-Leaved Pine 



Transverse. Growth rings thick. Summer wood thick, very prominent, 

 dense, and often exceeding the spring wood from which the transi- 

 tion is generally very abrupt ; the tracheids unequal in regular rows, 

 but varying greatly in different growth rings so that the structure 

 presents a very variable density. Spring tracheids large, squarish- 

 hexagonal, the walls thin. Resin passages numerous but large and 

 scattering; the epithelium composed of i row of thin-walled cells, less 

 frequently becoming 2-rowed in part, the cells often resinous. Medul- 

 lary rays prominent, rather broad, numerous, distant 2-8 rows of 

 tracheids. 



Radial. Rays somewhat resinous throughout ; the ray tracheids rather 

 high, conspicuously predominant and very strongly reticulated through- 

 out, often composing the entire ray. Ray cells of one kind, rarely of 

 two kinds, few, interspersed, fusiform ; the terminal, upper, and lower 

 walls very thin and much broken out; the lateral walls with very 

 variable, lenticular pits, 1-4 per tracheid, becoming more or less obso- 

 lete in the summer wood. Bordered pits in i row or pairs, rarely 

 2-rowed, elliptical, in the summer wood reduced to 7.2 fj., when the 

 orifice often becomes obscure or eccentric. Pits on the tangential 

 walls of the summer wood wholly wanting. 



Tangential. Fusiform rays rather numerous, high, the terminals prolonged, 

 linear, and composed of broad parenchyma cells with terminal tra- 

 cheids ; the cells of the inflated portion very thin-walled and usually 

 all broken out. Ordinary rays rather numerous, high, presenting two 

 principal aspects: (i) low rays composed of thin-walled parenchyma 

 much broken out, and small, terminal tracheids ; and (2) higher rays 

 composed of oblong tracheids with few, interspersed, broader cells of 

 thin-walled parenchyma, thus causing local expansions. 



A tree 24-30 m. in height, with a trunk upwards of 1.35 m. in diameter. 

 Wood varying greatly, heavy, hard, strong, generally coarse grained, and 

 compact. 



Specific gravity 0.6104 



Percentage of ash residue 0.29 



Approximate relative fuel value 60.86 



Coefficient of elasticity in kilograms on millimeters . . 1375. 



Ultimate transverse strength in kilograms 443. 



Ultimate resistance to longitudinal crushing in kilograms 7628. 



Resistance to indentation to 1.27 mm. in kilograms . . 2064. 

 (Sargent) 



