FOREST ENEMIES 187 



neighbors. They are ordinarily no great menace to a healthy 

 forest. And fortunately not all fungi attack living trees. Some, 

 on the other hand, perform a very useful function, for they 

 bring about the decay of dead wood in the forest and allow it 

 to rot back into the soil again. 



There are still other enemies. Mistletoe is a parasitic growth 

 that has caused great damage in the south and west especially 

 among the magnificent white oaks of California. Porcupines 

 should be numbered among our forest enemies, for many trees, 

 especially the western pines, have been stripped of their bark 

 by hungry porcupines. But most of these enemies beetles, leaf- 

 eaters, parasites, fungi except in periods of unusual activity 

 direct their attacks against trees already weak and many can 

 only gain their points of entrance where the bark has been 

 broken or where fires have burned. 



All this has emphasized to the forester the importance of 

 securing and maintaining a healthy forest a forest able to re- 

 sist attacks. For these enemies themselves are in league with 

 each other and create conditions that are mutually helpful. 

 Thus, the bark beetle weakens the tree and makes it more 

 vulnerable to the defoliators; a porcupine gnaws the bark and 

 allows entrance to some destructive fungus. 



In all this it is not well to let our view of the forest situation 

 become distorted. When we read of all these insects, fungi, 

 and parasites, all these living things that continually beset 

 the forest, the outlook for our future trees may seem black. 

 But here one should remember the tremendous vitality of na- 

 ture. To offset these innumerable enemies, the unpredictable 

 accidents, the hostile forces of earth and air, nature puts forth 

 a hundred thousand seeds in order to bring one tree to matur- 



