306 ANATOMY OF THE GYMNOSPERMS 



elliptical. Pits on the tangential walls of the summer wood rather 

 numerous, small and chiefly confined to the two outermost walls. Resin- 

 ous tracheids wanting. 



Tangential. Fusiform rays numerous, very narrow ; the cells of the inflated 

 portion all thin-walled and usually much broken out ; the somewhat 

 thicker-walled structure of the central tract generally present and 

 embracing a small resin canal. Ordinary rays sparingly resinous, 

 medium, numerous, broad, somewhat contracted by occasionally inter- 

 spersed, narrowly oval or oblong tracheids ; the thick-walled cells 

 usually equal and somewhat uniform, oval to oblong, rarely narrow. 

 Resinous tracheids wanting. 



A small tree 6-9 m. high, with a trunk upwards of .45 m. in diameter. 

 Wood light, soft, close grained, and compact. 



Relative specific gravity 0.5675 



Percentage of ash residue 0.54 



Approximate relative fuel value 56.44 



Coefficient of elasticity in kilograms on millimeters . . 378. 



Ultimate transverse strength in kilograms 182. 



Ultimate resistance to crushing in kilograms .... 5420. 



Resistance to indentation to 1.27 mm. in kilograms . . 3126. 

 (Sargent) 



Larkin's Station, San Diego County, California, and southward into Lower 

 California, where it forms extensive forests on high mesas and slopes 

 (Sargent). 



2. P. cembroides, Zucc. 



Pi noii. A'at Pine 



Transverse. Growth rings not broad, variable, more or less conspicuously 

 double, the structure as a whole rather dense. Summer wood rather 

 open, either very thin or upwards of equal to the spring wood, from 

 which the transition is very gradual and from which it cannot be 

 readily distinguished ; the tracheids distinctly rounded, unequal, but in 

 rather regular rows. Spring tracheids hexagonal, not large, very un- 

 equal and variable, but in regular rows. Medullary rays prominent 

 and numerous, broad, I cell wide, distant 1-6, rarely 10, rows of tra- 

 cheids. Resin passages numerous, not large, chiefly in the middle or 

 inner portion of the growth ring, the several-layered epithelium com- 

 posed of large, thick- and thin-walled, nonresinous cells. 



Radial. Rays somewhat resinous, the resin localized, granular, rarely mas- 

 sive ; the tracheids not very numerous, marginal, rarely interspersed ; 

 the lateral walls with very small pits about 2 per tracheid. Paren- 

 chyma ray cells conspicuously contracted at the ends throughout, 

 short, equal to 8-10 tracheids; the upper and lower walls thick, uni- 

 form, conspicuously pitted throughout : the terminal walls thin but 

 locally thickened or more often coarsely pitted ; the lateral walls with 

 small, round pits, with a more or less obvious though very unequal 

 border and a lenticular orifice, at first 2-4, but in the summer wood 



