SURROUNDINGS OF A TREE 21 



very nearly with those in the human blood. There are other 

 facts also which prove that some of the same chemical elements 

 found in the environment somehow or other become organized 

 into the tremendously complex material of which we find living 

 plants and animals composed. 



PROBLEM I. HOW IS A TREE FITTED TO LIVE IN ITS 

 NATURAL SURROUNDINGS? 



Field Exercise. Observe a tree in its natural environment. Bring in 

 all the information you can to class concerning where a given tree grows, 

 its form, size, characteristics, etc. The findings of the class can be 

 tabulated on the board, and from this a general statement can be made 

 concerning the characteristics of all trees. 



As Joyce Kilmer well said, there is no poem as lovely as a tree. 

 Trees are so commonplace that we are not likely to consider what 

 life would be without them. They grow straight and tall, even in 

 cities where life for them must be very difficult. The problem 

 before us is, " How do they do it ? " How can a tree (or any other 

 green plant for that matter) develop into the great bulk that they 

 have? They cannot make something out of nothing. It takes 

 several acorns to weigh an ounce, but an oak tree weighs several 

 tons. Where does this increase come from ? Evidently the young 

 tree must take something from its surroundings in order to grow. 

 What are the substances it uses? And how does it do this? 



The skeleton. Let us take a typical tree, such as the maple 

 or elm. We notice in winter it is a skeleton, a straight trunk or 

 main stem and many branching limbs which spread out into ever 

 smaller and smaller branches. These are covered with buds which 

 in spring will produce leaves or flowers or both. Under the 

 ground we know there are roots, which, in the same manner as the 

 branches, spread out widely and continually branch so that in 

 many trees there is almost as much of the tree below ground as 

 above it. Evidently the roots anchor the tree in the ground, 

 while the branches place the buds and leaves in the most favorable 

 position possible. 



Leaves. In the summer the tree is covered with green leaves. 

 These, we notice, are set as far out as possible on the branches. 

 Evidently sunlight influences them, for a bird's-eye view of the 

 H. bio — 3 



