SILVICaLTURAL SYSTEMS. 



31 



The conifers are the more viilual)le, and among them 

 the principal hmiber tree is the spruce. 



The Bureau of Forestr}^ 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 younger spruce will grow up 

 and replace the original stand of timber in about 

 twenty 3^ears. But this will not happen unless the 



Fig. 18.— Natural forest resembling Localized Selection. Southern Oregon. 



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 mav then be 

 divided into twenty parts, and the merchantable timber 

 about 12 inches in diameter mav safelv be cut from one 

 division every a ear. By the time the last of the twent}^ 

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

 a stand rtf mature spruce equal in quantit}^ to that of 



