48 EVERGREENS OF COLORADO 



while railway ties are made from the largest trees of this species. In the 

 lower foothills region, Douglas fir is extensively used for fence posts, for 

 which purpose its greater durability than some of the other of the native 

 species makes it well fitted. Limber pine and bristle-cone pine are used 

 to some extent for mine timbers, where these species occur in any con- 

 siderable quantity. Balsam fir, blue spruce and white fir are utilized to a 

 much less degree for the same purpose, the lack of durability of the fir 

 being one of the factors which has much to do with the slight use 

 made of it. 



Fig-. 32. White Fir. Portion of branch bearing nearly mature cones, x%. 



In the production of the so-called pitch pine fence posts, yellow pine 

 is practically the only species concerned. Pitch pine in this connection 

 has reference to the trunks of trees which have in some way become 

 heavily impregnated with the resinous juice from their own wood. Just 

 how this has been brought about is a matter of considerable uncertainty, 

 as it seems to be confined largely to individual trees and is not necessarily 

 a characteristic of the species. It has been commonly observed that any 

 wounds in the bark of trees which do not kill the tree at once, tend to 

 produce a strong flow of the resinous sap, which may be absorbed grad- 

 ually by the. wood itself and thereby greatly increase its durability. Some 

 persons claim to be able to produce pitch pine at will by peeling the Irve 

 trees and allowing them to stand for one or more seasons. In this way 

 the pitch which is freely produced on the surface, is reabsorbed in a large 

 measure and gives the timber its desired quality. The writer is unable to 

 substantiate such claims through any personal experiments or from sources 

 of reliable information. Such experiments, however, are being conducted 



