40 THE WORLD IX WHICH WE LIVE 



cut, the veins stand out more, and the skin of the leaf 

 is more porous. For even leaves have skin. The 

 outer covering of all leaves is a thin and transparent 

 membrane that does for the leaf what our skin does 

 for us. 



Some trees do not have all the sunlight they need. 

 Can you think what trees those are? Forest trees? 

 Yes, in the forest the sun can reach only the tops of 

 the trees. Have you ever noticed the difference 

 between a forest tree and the same kind of a tree 

 growing in the open field? The forest trees have tall, 

 straight, slender trunks, with no live branches upon 

 them except near the top of the tree. 



In the open field a tree has plenty of room and sun- 

 light and it grows into its own natural shape, with 

 great spreading branches, and with the whole body 

 of the tree covered with leaves. All those leaves have 

 sunlight, and the tree puts forth as many as the space 

 permits. But the forest tree can only get sunlight by 

 growing straight up toward it. If it does not reach 

 the light with its leaves it must die, because without 

 sunlight the leaves cannot provide the proper nour- 

 ishment for the tree. They would be like kitchens 

 without a fire! Some of the trees in the woods have 

 died for this reason. 



But the trees that grew straight up, reaching al- 

 ways for the sunlight, have lived. The lower 

 branches have died, and, as the trees grew older, have 

 fallen off and left the trunks tall and smooth almost 

 to the top. There at the top the leaves form a canopy 

 so thick that only little patches of sunUght ever reach 

 the forest floor. 



