EVERGREENS OF COLORADO 



29 



scattered freely over the surface, from which character is derived the 

 common name, balsam, often applied to the trees of this genus. The 

 bark on old trunks usually becomes roughened and more or less broken 

 into longitudinal ridges. 



The wood is mostly very soft, light and brittle and is not esteemed 

 by lumbermen. The cones occur only in the topmost parts of the trees 

 and stand erect on the upper side of the branches until mature, in which 

 respect these trees differ from the spruces and the Douglas fir. When 

 mature, the cones break up by the falling away of the scales and leave 

 the central axis of the cone in the form of a spike, which may remain 

 attached to the twig for some time. Complete cones of the firs are 

 consequently never found beneath the trees, unless they have been pre- 

 maturely removed by some accidental cause. 



The seeds are of fair size, nearly triangular in shape, and attached 



Fig. 18. Blue Spruce. Young pistillate cones pointing up- 

 ward, and mature cones hanging downward, x 1 ^. 



to broad, thin wings. They are scattered by the breaking up of the cones. 

 The balsam fir of the Northeastern states and Canada (Abies 

 balsamea) furnishes the substance known in commerce as Canada Balsam, 

 which is derived from the balsam blisters in the bark of this tree. Two 

 species of balsam firs are found growing in the mountains of Colorado. 



KEY TO THE SPECIES OF ABIES IN COLORADO. 



Needles (leaves) of vigorous lower branches one to one and three- 

 fourths inches long; the two resin tubes, as seen in cross section 

 under hand lens, deeply imbedded within the leaf tissue. Cones 

 purple or nearly black. 



1. Abies lasiocarpa. 



