PINUS 305 



Resin passages obliterated. 



Bordered pits on the lateral walls of the ray 

 cells 2-3 per tracheid. 



46. ** P. Peali. 



Bordered pits in 1-3, chiefly 2, rows, round or hexagonal. 

 Ordinary rays (tangential) 2-seriate in part. 

 Resin passages not represented. 



47. * * P. chasense. 

 Ray tracheids wholly wanting. 



Bordered pits in i row. 



Resin passages numerous, large, chiefly in the summer wood, 

 filled with prominent and resinous thyloses, the epithelium 

 1-2 cells thick, not extended into parenchymatous tracts. 



48. * * P. statenense. 



Resin passages numerous, small, chiefly in the summer wood, devoid 

 of thyloses, the epithelium composed of a single layer which ex- 

 tends into a prominent and often broad tract of wood parenchyma. 



49. ** P. scituatense. 



A. PINUS PROPER 



Existing Species 



Section I. Soft Pines 

 1. P. Parryana, Engelm. 



Pinon. Nut Pine 



Transverse. Growth rings chiefly narrow but very variable. Summer wood 

 very open and chiefly very thin, but in the broader rings upwards 

 of one half the spring wood, from which the transition is very gradual ; 

 the tracheids in regular rows, conspicuously unequal and rounded. 

 Spring tracheids squarish-hexagonal, unequal in regular rows, the walls 

 rather thin. Medullary rays numerous, broad, i cell wide, distant 2-6 

 rows of tracheids. Resin passages numerous, medium, and variable, 

 very scattering throughout the entire growth ring ; the several-layered 

 epithelium composed of very large, rather thick-walled cells, more or 

 less resinous. 



Radial. Rays sparingly resinous ; the tracheids numerous, marginal, high, 

 rarely interspersed. Parenchyma ray cells chiefly straight and rather 

 narrow, but in the narrower growth rings and in the summer wood 

 becoming shorter and distinctly fusiform ; the upper and lower walls 

 thick and conspicuously though often distantly pitted, becoming more 

 strongly pitted in the fusiform cells ; the terminal walls locally thick- 

 ened or coarsely pitted ; the lateral walls with small, round pits with 

 a more or less definite though variable border and a lenticular orifice, 

 2-4 per tracheid. Bordered pits in i row, rather numerous, broadly 



