SILYICL'LTURAL SYSTEMS. 



31 



The conifers are the more valual:>le, and among them 

 the principal lumber tree is the spruce. 



The Bureau of Forestry has found by many careful 

 measurements that if all spruce trees 1:^ inches and 

 over in diameter are cut from certain portions of the 

 Adirondack forest, the young-er spruce will grow up 

 and replace the original stand of timber in about 

 twent}^ 3^ears. But this will not happen unless the 



Fig. 18.— Natural forest resembling Localiztd > 



rules for cutting are faithfully observed, nor will it 

 happen more than once unless enough old trees are 

 left standing for seed. Such a forest may then be 

 divided into twenty parts, and the merchantable timber 

 about 12 inches in diameter ma}' safely be cut from one 

 division every year. Bv the time the last of the twent}^ 

 divisions has been cut over, the first will have upon it 

 a stand of mature spruce equal in quantity to that of 



