136 North American Forests and Forestry- 

 valuable kinds, and the removal of sickly or crippled 

 individuals that can never become good timber 

 producers and may even infect sound neighbors 

 with their own malady. There are certain rules 

 according to which the trees are allowed to grow 

 thickly together or farther apart, according to the 

 object aimed at in each particular time and place. 

 It is surprising to see the extent to which the 

 forester can regulate the manner of growth of 

 trees and the character of wood produced by them. 

 As a general thing saplings should grow close 

 together for a series of years. This forces them 

 upward into long, clean shafts with few branches. 

 Thereby clean, straight timber is produced. For 

 the presence of each branch produces a knot in the 

 lumber sawed from the log, and thereby reduces its 

 value. The longer a branch is allowed to grow, 

 the larger will be the knot. If the trees stand close 

 together, not only will fewer branches be formed, 

 but those existing on the lower parts of the trunk 

 will soon die off for want of light. This process is 

 technically called the cleaning of the shafts. 



After a number of years a time comes when 

 height growth is no longer the first thing to be 

 aimed at. The object now must be to cause the 

 young tree to increase the diameter of its trunk, 

 and thereby the size of the logs that will some day 

 be cut from it. In order to accomplish this, a por- 

 tion of the trees is removed, this giving the crowns 

 of the rest a chance to develop. With the broad- 

 ening and filling out of the crowns comes also an 



