124 PLANTS AND ANIMALS 



rain has ceased to fall, although the water which ran off 

 the bare ground during the rain may have caused floods. 

 If there are forests, however, the leaves gather much of 

 the rain and cause it to drip slowly to the ground. There 

 it is caught in the mass of dead leaves and twigs and 

 cannot run away. Thus it slowly sinks into the ground 

 until the soil is wet many feet deep. When the rain 

 ceases the sun cannot cause the water to evaporate 

 because the thick shade of the forest keeps it out. The 

 water slowly passes away by capillarity and thus the 

 streams and rivers flow for a long time. 



The government of the United States has set aside 

 vast forests called National Forests in order to regulate 

 the flow of water, as well as to keep up a supply of 

 wood. The older trees are cut and younger ones are 

 allowed to grow in their places. The chief enemies of 

 the forest are fire and insects. . Men, called Forest 

 Rangers, protect the trees against fire, and our friends 

 the woodpeckers, eat the insects. The illustration shows 

 how "frogstools" indicate that decay has begun. The 

 frogstools live upon the trees where insects have made 

 holes in the bark. Just as our skin protects us from 

 bacteria so the bark protects trees from decay. The 

 heart of a tree may be decayed and the tree will still live, 

 for its growth is on the outside. In what part of the 

 twigs did the red ink rise in Experiment 55? Each year 

 a ring is added around the trunk of a tree, unless decay 

 is taking place on the outside of it, and by counting the 

 rings on the stump of a tree which has been cut down you 

 can tell its age. 



Just as with flowers, we should know the common 

 trees by name. It is not possible to make a collection 



