PINUS 337 



33. P. scopulorum, Lemmon 



Transverse. Summer wood very variable, rather open, commonly double ; 

 the tracheids in very regular rows and uniform, but generally much com- 

 pressed ; the transition from the spring wood rather abrupt. Spring 

 tracheids conspicuously squarish, rather uniform in regular rows, large 

 and thin-walled. Resin passages rather numerous and scattering, not 

 large ; the epithelium nonresinous, composed of about 2 rows of very 

 large and very thin-walled cells, those of the limiting layer flattened, 

 those of the secondary layers round, merging into a few thick-walled, 

 round parenchyma cells on the borders of the wood tracheids. Medul- 

 lary rays rather broad, i cell wide, rather numerous but not prominent, 

 distant 2-10, more rarely 17, rows of tracheids. 



Radial. Rays nonresinous ; the ray tracheids commonly high, marginal, or 

 becoming interspersed in the higher rays, predominant and sparingly 

 reticulated. Ray cells of two kinds: (i) the terminal walls thin and 

 locally thickened ; the upper and lower walls thick and strongly pitted ; 

 the lateral walls with round, simple pits 1-4 per tracheid, conterminous 

 and interspersed with those of the second order ; and (2) the terminal, 

 upper, and lower walls thin and not pitted or locally thickened ; the 

 lateral walls with small, lenticular pits, 2-4, chiefly 4, per tracheid, 

 becoming i or 2 in the summer wood. Bordered pits in i row, 

 numerous, crowded, elliptical. Pits on the tangential walls of the 

 summer w r ood wholly wanting. 



Tangential. Fusiform rays not numerous, narrow ; the somewhat prolonged 

 terminals composed of tracheids ; the inflated portion composed of very 

 thin-walled cells, usually all broken out. Ordinary rays rather numerous, 

 low to medium, nonresinous, conspicuously contracted by the somewhat 

 narrower, sometimes interspersed, and conspicuously predominant tra- 

 cheids ; the thick-walled parenchyma cells few, not prominent, the thin- 

 walled parenchyma cells occupying the central tract, oval, variable. 



34. P. pungens, Michx. f. 



Table Mountain Pine. Hickory Pine 



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

 sometimes somewhat open, often double, the transition from the spring 

 wood gradual, sometimes abrupt ; the tracheids in regular rows, vari- 

 able, rounded. Spring tracheids strongly hexagonal, very unequal in 

 regular rows, the walls rather thick. Resin passages rather large, 

 numerous, chiefly ill the summer wood ; the epithelium in i row of 

 very thin-walled and nonresinous cells, rarely much exceeding the canal 

 and forming eccentric tracts of limited extent. Medullary rays rather 

 broad, somewhat prominent, numerous, distant 2-15 rows of tracheids. 



Radial. Rays somewhat resinous throughout ; the tracheids variable, often 

 predominant, reticulated throughout and more or less interspersed. 

 Ray cells of two kinds : (i) cells numerous and long fusiform ; the ter- 

 minal walls entire or locally thickened ; the upper and lower walls 

 strongly thickened and coarsely pitted ; the lateral walls with very vari- 

 able, oval, or lenticular pits, 1-3 per tracheid, in the summer wood 

 distinctly bordered, the orifice a prolonged slit ; and (2) cells variously 



