Il6 UNIVERSITY OF COLORADO STUDIES 



pellate flowers solitary or clustered. Cone scales thick, becoming woody; bracts 

 short in comparison with the scales. The cones ripen the second year or later. 

 The genus Pinus is widely distributed throughout the northern hemisphere and 

 extends to the Philippine Islands and Sumatra. In the United States and British 

 North America there are about 36 species. 



Key to the Colorado Species of the Genus Pinus 



A. Leaves in bundles of 4 to 6; medium sized or small trees, chiefly in high alti- 

 tudes. 



a. Leaves 25 to 40 mm. (i to if in.) long. Cones 7 to 9 cm. (af to 32 in.) long, 

 the scales with curved, needle-pointed spines. i. Pinus aristata 



b. Leaves 3.5 to 7.5 cm. (i| to 3 in.) long. Tree of wind-swept mountain 

 sides or exposed points. Cones large, 7 to 25 cm. (af to 9I in.) long, the 

 scales smooth, without spines. 2. Pinus flexilis 



B. Leaves in bundles of 2 or 3. 



a. Leaves short, 2 to 4 cm. (| to ij in.) long generally in pairs; cones small, 

 about the same length as the leaves, seeds large (about the size of a common 

 white bean), edible. A tree or shrub found in the foothills south and west. 



3. Pinus edulis' 



b. Leaves longer, 4 to 12 cm. (ij to 4! in.) long; in bundles of 2 or 3. 



a' Leaves usually about 10 cm. (3J in.) long, but shorter in exposed situa- 

 tions; sometimes longer. Cones 6 to 9 cm. (2! to 32 in.). A tree of 

 foothills and river bluffs and extending to an altitude of 10,000 ft. 



4. Pinus scopulorum 



b' Leaves 3 to 6 cm. (i| to 2I in.) long; cones about same length as leaves. 

 A tree of foothills and mountains, often forming pure forests at altitudes 

 of 7,000 to 9,000 ft. 5. Pinus murrayana 



Pinus aristata Engelm. Bristle-cone Pine 



Rydberg, Flora Colo. 7; Coulter, Manual 432 (as P. haljouriana, var. aristata); 

 Sargent, Manual Trees of N. A. 9. 



Leaves in bundles of 4 or 5, dark green, 2.5 to 4 cm. long. Staminatc flowers 

 dark orange-red; carpellate dark purple. Cone 7 to 9 cm. long. Cone scales 

 somewhat thin, each with a slender curved bristle about 6 mm. long. Seeds winged. 



A bushy tree of small or medium size with the main trunk short, numerous 

 strong branches starting rather low down. Bark thin, pale or milky white on small 

 branchlets, dark gray or brown on the main trunk. Wood soft and not durable; 

 specific gravity 0.5572. Sometimes used for fuel. Formerly much employed in 

 central Nevada for mine timbers but the supply is now nearly exhausted. 



Rocky and gravelly slopes at high altitudes in the mountains from central and 

 southern Colorado to Utah, Nevada, southern California and Arizona. 



' A related species, Pinus monophylla, differing in having the leaves single, is reported in Rydberg's 

 Flora of Colorado from Manitou. The species, is however, usually considered to range west of Colorado. 



