32 FOREST TREE DISEASES. 



100 per cent of mature incense cedar is affected with 

 dry rot. The same is true, although not always to the 

 same extent, of white fir and red fir. 



The fungi of this group are all more or less closely 

 related to one another. Their fruiting bodies are usu- 

 ally large and conspicuous, and appear in the shape of 

 conchs, shelves, toadstools, or crusts (see p. 29). Some 

 develop fruiting bodies on the living tree, others after 

 the death of their victim, or on both the living and the 

 dead tree. 



DISEASES OF FOLIAGE, TWIGS, AND BRANCHES. 

 EFFECT. 



Needle and leaf, twig and branch diseases affect the 

 prospective value of growing trees that is, the future 

 crop since they interfere with the production of mer- 

 chantable timber; wood-destroying fungi, on the other 

 hand, endanger our present capital of timber. The 

 diseases of the foliage, twigs, and branches are more 

 dangerous to immature than to mature trees. If only 

 a few leaves and branches are killed, others replace 

 them, or their functions are taken over by those that 

 remain. When, however, the damage is considerable, 

 the remaining organs are not able to assume the whole 

 work, and the equilibrium between foliage and root 

 system is seriously disturbed. Growth is retarded, and 

 the tree may eventually die. If this should happen 

 before the tree is ready for the ax, the loss in expected 

 timber is complete. Should an old tree die from the 

 attack of these fungi, on the other hand, the damage 



