122 UNIVERSITY OF COLORADO STUDIES 



distinct balsam blisters are found in the bark which contain the substance known as 

 "Canada balsam." Only two species of Abies are known in Colorado. 



Key to the Species of Abies in Colorado 



A. Leaves of vigorous lower branches 2.5 to 4.5 cm (i to ij in.) long; resin ducts 

 of the leaves deeply imbedded, not close to the epidermis. Cones purple or 

 nearly black. i. Abies lasiocarpa 



B. Leaves of vigorous lower branches 4.5 to 7.5 cm. (if to 3 in.) long; resin ducts 

 of the leaves close to the epidermis of the under surface; cones yellow, green or 

 purple. Not found in northern Colorado. 2. Abies concolor 



Abies lasiocarpa (Hook.) Nutt. Alpine Fir 



Rydberg, Flora Colo. 9; Coulter, Manual 430 (as Abies subalpina); Sargent, 

 Manual Trees of N.A. 61. 



Leaves flat, with prominent mid-vein, bluish-green; on vigorous lower branches 

 2.5 to 4.5 cm. long; on old parts and on cone-bearing twigs much shorter. Cone 

 oblong-cylindrical, rounded, erect, purple or nearly black, 6 to 10 cm. long. 



A medium sized tree with branches extending nearly to the base of the trunk; 

 bark of young trees pale gray and smooth; on old trees broken with shallow fissures 

 and roughened with thin orange-colored scales. Wood light, not strong, nor durable; 

 of little value but sometimes used as firewood; specific gravity 0.3476. 



High altitudes in the mountains throughout western North America. 



This species is sometimes planted as an ornamental tree in the northern United 

 States and in central Europe. 



Abies concolor Lindl. White Fir 



Rydberg, Flora Colo. 9; Coulter. Manual 430; Sargent, Manual Trees 0} 

 N. A. 62. 



Leaves mostly in two rows on the branchlets, more or less erect; on lower 

 branches flat, straight, with rounded or pointed apex; length 4.5 to 7.5 cm.; on 

 cone-bearing twigs shorter and generally curved. Cone ellipsoid-cylindrical, 7 to 

 13 cm. long, grayish-green, purple or yellow, with broad, closely imbricated scales. 

 A large tree with narrow spirelike crown; the short, main branches bearing long, 

 lateral branchlets; the whole forming frondlike masses of foliage. Bark of old 

 trunks becoming very thick, deeply divided into broad, rounded ridges. Wood 

 light, close grained, not strong nor durable; specific gravity 0.3638. 



From the Pike's Peak region of the Rocky Mountains of Colorado west to Ore- 

 gon and south to northern Mexico and Arizona reaching its greatest development 

 in the Sierras of California. It is the only true fir in the arid regions of the great 

 Basin. 



This tree has been planted for ornament in some places and promises to be 

 useful. 



