THE SILVA OF COLORADO II3 



and dry up so that they are not seen except in spring and early summer. 

 Members of the pine family are easily recognized by the needle-Hke 

 leaves. The Colorado species, and in fact nearly all cone-bearers are 

 evergreen. This condition is, however, not an essential in the family, for 

 the larches, or tamaracks, of the northern states are deciduous. Through- 

 out the northern hemisphere the pines and their allies are the most 

 important of all woods for building purposes. The wood of the true 

 pines is the most generally used. Two distinct kinds of pines are 

 recognized, viz.: the hard pines or "yellow pines" and the soft pines, 

 "white pines." Douglas spruce ("red fir" "Oregon pine") has wood 

 resembling the hard pines in quality. Firs and true spruces have 

 inferior wood. In fact, the wood of trees in the highest mountains is 

 generally not strong but light and brittle. This fact is easily under- 

 stood when it is known that the hard part of wood is that formed in 

 the summer. Tropical woods are often hard and heavy. Trees of 

 mountain tops — the spruces and firs — do not exist in conditions of 

 summer and hence do not develop hard and strong wood. Spruce is, 

 however, valuable as a source of wood pulp for making paper. The 

 wood of all the trees of the pine family is known as "non-porous" 

 because there are no vessels, or "pores" in it. Like the hardwoods 

 it is most durable when "quarter-sawed." 



Species of the pine family in Colorado. — Ten species are known in 

 Colorado. Of these there are five' pines, two true spruces, one Douglas 

 spruce and two firs. The four genera are easily distinguished and it 

 is not difficult to recognize most of the species. However, very few 

 residents of the state and still fewer visitors know them apart. In fact 

 it is quite common to hear them all called pines. It is hoped that 

 the following keys and descriptions will be useful to those interested. 

 There is no good reason why miners, engineers and citizens generally 

 should not know our forest trees. 



How to use the key and descriptions. — First be sure that the speci- 

 men to be examined is one of the pine family (with needle leaves). 

 These keys and descriptions do not include any account of the junipers 



' Rydberg in the Flora of Colorado credits the state with one more species of true pine, but I have 

 omitted a description of it since its occurrence is somewhat doubtful. 



