132 FIRST BOOK (JF FORESTRY 



is necessary that the wood of dead trees be converted into 

 dust to prevent the ground from becoming covered with 

 dead timber. Such a cover would bring all forest grow^th 

 to a standstill, there would no longer be room for trees, 

 and its destruction by fungi, therefore, is useful. It is 

 Nature's way of clearing the ground for new generations 

 of trees. But, like many useful things, these fungi overdo 

 their work, and at the slightest provocation attack good, 

 thrifty trees. Thus, if a wind tears off the large limb of 

 a maple, beech, birch, poplar, or other perishable kind of 

 tree, fungi at once begin their work of destruction ; the 

 interior begins to decay; limbs and stem are hollowed out; 

 the tree is weakened and becomes an easy prey to bark 

 beetles or a storm. Once on the ground, a few years in 

 our moister districts suffice to convert the trunk and all 

 into a powdery mass of decayed wood, which is spread out 

 by insects and w^ater, and thus helps to improve the soil 

 for a new growth. Though the trees with perishable 

 woods are more subject to this injury than those in which 

 resin and other substances make the w^ood more durable, 

 yet all kinds of our trees suffer more or less. Thus, even 

 the durable cypress is injured by a fungus, which causes 

 it to become " pecky," and our white cedars are generally 

 •' hollow butted," the stump being decayed so much that 

 it is a common defect of cedar timber. 



From this it appears that clean w^oods, composed of 

 thrifty, uninjured trees, suffer much less from injurious 



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