OUR FORESTS 



139 



fibers not taking straight lines in their course in the tree trunk. Tn many 

 cases the fibers of the wood take a spiral course up the trunk, or they 

 may wave outward to form little projections. Boards cut out of such a 

 piece of wood will show the effect seen in many of 

 the school desks, where the annual rings appear to 

 form elliptical markings. 



Knots. Knots, as can be seen from the diagram, 

 are branches which at one time started in their 

 outward growth and were for some reason killed. 

 Later, the tree, continuing in its outward growth, 

 surrounded them and covered them up. A dead 

 limb should be pruned before such growth occurs. 

 The markings in bird's-eye maple are caused by 

 adventitious buds which have not developed, and 

 have been overgrown with the wood of the tree. 



Section of tree trunk 

 showing knot. 



Destruction of the Forest. By Waste in Cutting. Man is 

 responsible for the destruction of one of this nation's most valuable 

 assets. This is primarily due to wrong and wasteful lumbering. 



A forest in the far West totally destroyed by fire and wasteful lumbering. 



Hundreds of thousands of dollars' worth of lumber is left to rot an- 

 nually because the lumbermen do not cut the trees close enough to 

 the ground, or because through careless felling of trees many other 



