16 FIRST BOOK OF FORESTRY 



yard ; and several smaller ones are dead among them, so 

 that there were even more some years ago ! But all 

 of these can never hope to live and grow to any great 

 size. Here is evidently a struggle ; most of the trees 

 must die, and those left must be injured by this struggle; 

 for the trees which will die during the next ten years are, 

 still using up food and water, much of which is needed by 

 those which will survive, and the crowns of these latter 

 are crowded and thus prevented from becoming as large 

 as they should be. 



Here is an old thicket twenty to thirty feet high, and 

 instead of as many as eight trees to a square yard, there 

 are little more than this number per square rod. These 

 saplings are slender poles, with little short crowns of live 

 limbs, and the greater part of the pole is bare ; the few 

 remaining lower limbs are all dead, most of them decayed 

 and broken. What has become of the limbs ? The dense 

 shade has prevented them from producing leaves, and as 

 soon as a limb ceases to produce leaves the tree ceases to 

 feed it ; it dies, dries, decays, and drops off . These sap- 

 lings have cleaned themselves and are still continuing to 

 do so. Now we understand why the large, long-shafted 

 trees we saw on our first trip have the fine, clear trunks 

 and make such good saw-logs. 



Without this cleaning our lumber would be far more 

 knotty than it is. Shading and crowding, then, help as 

 well as hurt in our forests. They help by killing out the 



