424 ELEMENTARY STUDIES IN BOTANY 



these are the accidents of nature that involve only a repair 

 of the damage. 



There are many insects which are very destructive to trees 

 because they bore into the wood or eat the leaves. The 

 gipsy moth has become famous for its leaf -destroying powers. 

 The best protection against insects is to encourage their 

 enemies. A forest full of birds, toads, snakes, etc., is well- 

 protected against destructive insects. The need for such 

 protection justifies the exclusion of hunters from forests under 

 cultivation, especially the men who shoot at everything. 



The problem of grazing animals in a forest is a mixed one. 

 These animals are usually sheep, and up to a certain num- 

 ber they may not be injurious, and may even be helpful, 

 but in large numbers they are injurious, being not only 

 grazing but also browsing animals. 



The danger to forests from plant diseases will be con- 

 sidered in the next chapter, which deals with plant diseases 

 in general. 



131. Forest products. It is a surprise to many to dis- 

 cover the number of uses to which forest trees are put. 

 Most people probably think of forests only as a source of 

 lumber, so far as their commercial use is concerned. It is 

 true that lumber is the conspicuous product, arid it is known 

 that this lumber is put to endless uses. For this purpose, 

 trees are grouped as " soft woods " (pine, spruce, hemlock, 

 cedar, etc.), belonging to the conifer group (called " ever- 

 greens " by many), and " hard woods " (oak, walnut, hickory, 

 cherry, locust, tulip-tree, ash, maple, elm, cottonwood, etc.). 

 The lumber industry in soft woods may be used as an illus- 

 tration. The most prized soft wood is the white pine, and 

 the important white pine states are Michigan, Wisconsin, 

 and Minnesota. This valuable tree has been harvested so 

 recklessly that it has now approached dangerously near the 

 point of extinction as a commercial source of lumber. The 

 lumber camps, logging operations, and the floating out of 



