238 STUDIES OF TREES 



details extending to greater differences which distinguish 

 one species from another. 



The lesson might continue by pointing out the require- 

 ments of trees for water and light. Find a tree on some 

 slope where the roots are exposed and another which is 

 being encroached upon by its neighbor, and show how in 

 one case the roots travel in search of water and food and 

 in the other the branches bend toward the light, growing 

 more vigorously on that side. Compare the trees on the 

 open lawn with those in the grove and show how those in 

 the open have grown with branches near the ground while 

 those in the woodland are slender, tall and free from 

 branches to some distance above the ground. Point out 

 the lenticels on the bark of birch and sweet cherry trees 

 and explain how trees breathe. Compare this process 

 with that of the human body. You may now come across 

 an old stump and here you can point out the structure of 

 the wood the sapwood, cambium and bark. You can 

 illustrate the annual rings and count the age of the tree. 

 At another point you may find a tree with a w r ound or 

 bruised bark and here you can readily make a closer study 

 of the cambium layer and its manner of growth. 



The adaptation of plants to the seasonal changes opens 

 another interesting field of study for beginners. If the 

 season is the fall or winter, note how the trees have pre- 

 pared themselves for the winter's cold by terminating the 

 flow of sap, by dropping their leaves too tender to resist 

 the winter's cold, and by covering their buds with scales 

 lined with down on the inside. Observe how the insects 

 have spun for themselves silken nests or remain preserved 

 in the egg state over the winter. If the season is spring or 

 summer the opposite may be noted. See how everything 

 turns to life; how the buds are opening, the leaves 



