112 OUR FORESTS 



taking straight lines in their course in the tree trunk. In 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^he effect seen in many of the school 

 desks, where the annual rings appear to form ellip- 

 tical markings. Quite a difference in color and 

 structure is often seen between the heartwood, 

 composed of the dead walls 01 cells occupying the 

 central part of the tree trunk, and the sapwood, 

 the living part of the stem. 



Knots. Knots, as can be seen from the dia- 

 gram, are branches which at one time started in 

 Section of a tree trunk their outward growth and were for some reason 

 showing knot. 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 buds which have not developed, and 

 have been overgrown with the wood of the tree. 



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. 

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

 annually because the lumbermen do not cut the trees close enough 

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

 other smaller trees are injured. There is great waste in the mills. 

 In fact, man wastes in every step from the forest to the finished 

 product. 



By Fire. Indirectly, man is responsible for fire, one of the 

 greatest enemies of the forest. Most of the great forest fires of 

 recent years, the losses from which total in the hundreds of mil- 

 lions, have been due either to railroads or to carelessness in making 

 fires in the woods. It is estimated that in forest lands traversed 

 by railroads from 25 per cent to 90 per cent of the fires are caused 

 by coal-burning locomotives. For this reason laws have been made 

 in New York State requiring locomotives passing through the 

 Adirondack forest preserve to burn oil instead of coal. This 

 has resulted in a considerable reduction in the number of fires. In 

 addition to the loss in timber, the fires often burn out the organic 



