10 



tain more of the dark-colored, flinty summer wood, which gives the 

 name " red " fir. Since trees ordinarily grow most rapidly in youth 

 and fall off with advancing age, " red " firs are apt to become 

 " yellow " firs as they grow older and the annual rings become nar- 

 rower. In old trees the rings are wider near the top than at the 

 stump, and old " j^ellow " firs are thus often found which contain red 

 wood at the center and top while the rest of the wood is yellow. 

 Slight differences in the texture of the bark, which accompany this 



Fig. 2. — Cones of the Rocky Mountain and coast forms of Douglas fir. The cone of the 

 former is smaller and more evenly conical, and has its bracts more projecting and re- 

 flexed. 



difference in rate of growth, often make it possible to distinguish in 

 the forest between " red " and " yelloAV " firs. 



The mountain form exhibits no such difference, but although it is 

 often of slow growth it produces a red wood, with usually a large 

 proportion of summer wood. It is neither as straight-grained nor 

 as easily worked as the coast fir, but is highly valued for its strength 

 and its durability in contact with the soil, in which respects it sur- 

 passes the other species with which it grows. 



[Cir. 150] 



