other trees and many shrubs and weeds start life with 

 a robustness that seems indestructible. Examples of 

 such early vigor are furnished by poplars, willows, 

 burdock, fireweed. 



The roots of seedling evergreen often fail to reach 

 the soil through the layer of dead leaves and moss, 

 and in those cases the seedling perishes. 



During the first few years of a tree's life, mice, 

 rabbits and deer are a source of danger to the tender 

 plant. They may eat it bodily or cripple it so badly 

 that other trees or various kind of brush choke it to 

 death. If the young tree escapes all these risks, it is 

 still in danger of any light running ground fire till 

 it is about thirty years old, when its bark is thick 

 enough to protect the living itssue beneath against 

 light fires. 



The worst enemy of trees is a wind-driven crown 

 fire ; against this all trees are helpless. If the tree 

 comes through all these dangers and survives attacks 

 of insects and fungi, so that it finally stands like a 

 landmark taller than all its neighbors, then it be- 

 comes exposed to the full violence of storms and to 

 the bolts from the clouds. 



Some of the old time lumbermen had the idea that 

 the white pine would not reproduce itself, but would 

 be followed by jack pine. The fact is that both white 

 pine and Norway pine abundantly reproduce their 

 kind, although it is true that large areas originally 

 covered by great pine trees show absolutely no growth 

 of whites or Norways, but are covered with poplars, 

 brush and jack pine. The true explanation of this 

 condition is that lumbering operations, where the 



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