THE SILVA OF COLORADO 263 



samic resin. The cone-scales and bracts separate from the axis while this 

 is still on the tree; hence complete cones are never found under the 

 trees. 



ia. Leaves of vigorous lower branches 2 .5 to 4.5 cm. (1 to if in.) long; resin ducts of the 

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



Abies lasiocarpa 



lb. 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. Abies concolor 



Abies lasiocarpa (Hook.) Nutt. Sub-alpine Fir. 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 rough- 

 ened 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. 



Abies concolor Lindl. White Fir. Leaves mostly in two rows on the branch- 

 lets, 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 imbri- 

 cated scales. A large tree with narrow spire-like crown; the short, main branches bearing 

 long, lateral branchlets; the whole forming frond-like 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 Oregon 

 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. 



Genus 5. SABINA, Cedar 



The trees and shrubs of this genus are often classified with the 

 junipers and placed in the genus Juniperus. It seems best to separate 

 them because the cedars have such a very different general appearance. 

 Leaves of true junipers are sharp-pointed and awl-shaped; instead of 

 being scale-like and rather soft to the touch, as are the leaves of cedars. 

 It is to be noted, however, that the leaves of young cedars are sharp- 

 pointed and look like the leaves of junipers. 



ia. Fruit when ripe blue, juicy, resinous. (2) 



lb. Fruit when ripe reddish-brown, dry, fibrous. Small tree of western Colorado and 

 westward. Sabina utahensis (Engelm.) Rydb. 



