24 Our Field and Forest Trees 



In a close wood many of the under branches die 

 for want of air and light, and we can see all the 

 trunks marked by scars where boughs have fallen, 

 and disfigured by dead branches which still cling 

 to their hold. 



The old trees of a dense wood can lift their 

 heads so far to find the sunshine because they have 

 lost most of their side branches by natural prun- 

 ing, and so all their force is spent in growing 

 upward. 



Let us see how nature prunes. When spring 

 comes and the trees wake to active life, a new 

 layer of young wood is spread over the living 

 trunk and branches, but none is being made on 

 the dead bough (Fig. lo). So there is a hole in 

 the new live wood with the dead bough sticking 

 through it. The edges of this hole make a sort 

 of collar around the base of the dead branch, and 

 as spring follows spring, and a new layer of wood 

 is added each year, the collar grows tighter and 

 tighter. At last the pressure of the young wood 

 becomes so strong, and the old dead wood is 

 pinched so hard, that it is just ready to snap. A 

 gust of wind, an ice storm, or even the pull of its 

 own dead weight may break the branch away 

 from the trunk. There is left the stub of the 

 cast-off branch, a disc of dead wood surrounded 

 by a ring of young living wood. If the tree thrives, 

 new wood and new bark are made each spring all 

 around the inside of the ring until the place 



