1 6 North American Forests and Forestry 



when the present generation of trees has run its 

 course, unless man interferes. The red and black 

 oaks are gradually supplanting the white oaks in 

 many parts of the country. 



We have repeatedly used the terms warfare and 

 fighting for the competition of trees among them- 

 selves, and it is time to give the reader an idea of 

 how such warfare is going on. Trees have no 

 claws and teeth with which they can attack each 

 other as animals do, but they can fight, neverthe- 

 less, and the numbers of the dead and crippled in 

 these battles are tremendous. 



There are two things which every tree needs, or 

 it must die : moisture for its roots, to carry water 

 containing in solution various mineral salts to all 

 parts of its body , and light to enable the leaves 

 to assimilate the material so furnished, and build 

 up the various vegetable tissues making up the 

 tree. Each kind of tree, by reason of its specific 

 characteristics, requires these two things in vary- 

 ing proportions. For each species there is a mini- 

 mum of light, and the accompanying warmth, and 

 also a maximum ; exceeding these limits, suffering 

 begins. The same holds true of moisture, as well 

 as some other requisites. For instance, most trees 

 will die if their roots are immersed in water for a 

 large part of the growing season. But a few, like 

 the black ash or bald cypress, will grow lustily on 

 swamps wet the year through. They have a very 

 high moisture maximum. On the other hand, 

 these species would not flourish on a dry, rocky 



