THE SILVA OF COLORADO 259 



Genus i. PINUS, Pine 

 Evergreen trees and shrubs growing often in dry and rocky situations. 

 Foliage leaves needle-shaped growing usually in bundles of 2 to 5 

 leaves. The foliage leaves are borne on very short twigs (dwarf shoots), 

 which arise in the axils of appressed scale leaves. Staminate cones 

 small, yellow or reddish, growing in clusters and shedding their pollen 

 in late spring or early summer. Carpellate cones either solitary or 

 clustered. Cone scales thick, becoming woody. The cones ripen the 

 second year or later. 



1 a. Leaves in bundles of 4 to 6; medium-sized or small trees, chiefly in high altitudes. 



(2) 



lb. Leaves in bundles of 2 or 3. (3) 



2a. Leaves 25 to 40 mm. (1 to if in.) long. Cones 7 to 9 cm. (2f to 3^ in.) long, the 

 scales with curved, needle-pointed spines. Pinus aristata 



2b. Leaves 3.5 to 7.5 cm. (if to 3 in.) long. Tree of wind-swept mountain sides or 

 exposed points. Cones large, 7 to 25 cm. (2f to of in.) long, the scales smooth, 

 without spines Pinus flexilis 



3a. Leaves short, 2 to 4 cm. (f to ii 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. Pinus edulis 



3b. Leaves longer, 4 to 12 cm. (i£ to 4f in.) long; in bundles of 2 or 3. (4) 



4a. Leaves usually about 10 cm. (3^ in.) long, but shorter in exposed situations; some- 

 times longer. Cones 6 to 9 cm. (2$ to 3^ in.). A tree of foothills and river bluffs 

 and extending occasionally to an altitude of 10,000 ft. Pinus scopulorum 



4b. Leaves 3 to 6 cm. (i£ to 2f in.) long; cones about same length as leaves. A tree of 

 foothills and mountains, often forming pure forests at altitudes of 7,500 to 9,500 ft. 



Pinus murrayana 



Pinus aristata Engelm. Bristle-cone Pine. Leaves in bundles of 4 or 5, 

 dark green, 2.5 to 4 cm. long. 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- 



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

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



Pinus flexilis James. Limber Pine, White Pine. Leaves in bundles of 5; 

 stout, rigid, dark green, 3.5 to 7.5 cm. long. Cone very large, 7 to 25 cm. long. Cone 

 scales smooth, without bristle points. Seeds large, with a narrow wing which usually 

 adheres to the cone scale when the seeds drop. 



A medium-sized tree with a short main trunk and abundant lateral branches, growing 

 in wind-swept situations and hence often much distorted. Bark of twigs and branches 

 pale gray or whitish, becoming dark brown on older trunks. Wood light; specific gravity 

 0.4358; sometimes used for lumber which is, however, full of knots. 



