SILVICULTURAL SYSTEMS. 



31 



The conifers are the more valuable, 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 12 inches and 

 over in diameter are cut from certain portions of the 

 Adirondack forest, the younger spruce will grow up 

 arid replace the original stand of timber in about 

 twenty years. 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 may then be 

 divided into twenty parts, and the merchantable timber 

 about 12 inches in diameter may safely be cut from one 

 division eveiy year. By the time the last of the twenty 

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

 a stand of mature spruce equal in quantity to that of 



