TREES 



369 



top each other. The one that succeeds will get most light, 

 and therefore grow the best. In the forest the lower branches 

 of the trees are killed by the shade of other trees, and in time 

 they fall off. The wound left by the branch, the knot hole, 

 generally heals over with a new layer of wood and bark. 

 In the forest the lower branches may not be within thirty 



Fig. 158. An Open Grove of H;ird Maples. 

 (The trees have rounded crowns, low branches.) 



or forty feet of the ground, while in 

 would have had a short thick trunk 

 low, and rounded crown. 



For the first ten years, the rate of 

 It is most rapid for several decades 

 again later. How long do trees live 

 the species. Some, hke the poplars, 

 dred to a hundred and fifty years. 



the open the same tree 

 with branches growing 



growth of trees is slow. 



after this, and slower 

 ? That depends upon 

 are short lived, a hun- 



Maples and oaks live 



