3 



I. PiNUS FLEXiLis James, Long's Exp, 2: 34. 1823. 



Tree 12-25 ni- high, trunk 5-10 dm. in diameter, bark grayish; 

 leaves in fascicles of 5, 4-7 cm. long; cones narrowly ovoid to 

 subcylindrical, greenish or light brown, 8-15 cm. long; the 

 scales unarmed, broad, slightly thickened at ends, opening at 

 maturity. Limber Pine. 



Rather common on ridges and slopes; 7,000-10,000 ft. (See 

 note under P. alhicaulis.) 



2. PiNUS ALBiCAULis Engelmann, Trans. Acad. Sci. St. Louis 2: 



209. 1868. 



Very similar to the preceding; cones oval or subglobose, 

 sessile, dark purple, 5-10 cm. long; the scales with thickened 

 ends, remaining closed at maturity. White-bark Pine. (See 

 also No. I, P. flexilis.) 



This and the preceding species are very closely related; in 

 fact, Engelmann in Watson's Botany of California, II, makes 

 P. alhicaulis a variety of P. flexilis. In the cross-sections (see 

 figures), P. flexilis usually lacks the resin duct in the angle 

 between the ventral sides, although some of the specimens of 

 this species appear to have it constantly. The two species 

 can best be distinguished by their cones, the most noticeable 

 and constant difference. Specimens without cones are readily 

 confused. 



3. PiNUS ARiSTATA Engelmann, Am. Journ. Sci. II. 34: 331. 



1862. 



12-15 m. high, 4-7 dm. in diameter; leaves in fascicles of 5, 

 submucronate, green, with a white glaucous stripe on each side; 

 cones violet-brown, narrowly ovoid, 7-10 cm. long; scales with 

 thickened rhombic ends, with small beak and tipped with a 

 lanceolate-subulate often recurved awn. Bristle-cone Pine. 



Subalpine; from Colorado south, and west- to California. 



This can be readily distinguished from the others of this 

 group by the lack of stomata on the outer side, and the deeply 

 sunken stomata on the ventral sides. Sometimes only one 

 resin duct is present. 



