376 



GENERAL BOTANY 



character of the wood elements which make up the bulk of the 

 wood. The student will recall that in spruce wood (Fig. 193) 

 the water-carrying elements were the one-celled, thick-walled 

 tracheids instead of the wide ducts of the alder and other hard 

 woods. The small diameter of these tracheids, their thick walls, 

 and their uniform size throughout the tree trunk make the 

 even, fine-grained wood of the spruces and other conifers, 

 like the white pine, extremely valuable in the industries. 



FIG. 229. Regrowth of aspen and spruce on a burned area in the San Francisco 

 Mountains, Arizona 



Photograph furnished by the United States Forest Service 



The long, fibrous character of these tracheids and their close 

 union with each other also contribute to their great value in 

 the wood-pulp industry and in the making of aeroplanes from 

 the now famous Sitka spruce. " Spruce is an aristocrat among 

 woods. Its outstanding characteristics are combined elasticity 

 and the ability to withstand sudden strain and shock." 



The most extensive use of spruce at the present time is in 

 the making of wood pulp for newspaper stock. Something 



