CHAPTER XVIIl 

 TREES 



Trees are the giants of the plant world. They consti- 

 tute a large element in the beauty and grandeur of the land- 

 scape, and they have always had a great influence upon 

 man's existence and his development. 



The tree should be studied as a flowering plant. As such 

 it has the usual organs and functions. 



Trees send their roots into the soil for anchorage and for 

 the soluble minerals and water. Some have large tap roots 

 that strike deep into the ground, the oak and butternut, for 

 example. Others, like the spruce and birch, let the roots run 

 out laterally not far beneath the surface. Hence they are 

 easily uprooted in storms, while the oak proverbially with- 

 stands the blasts. The root extent of trees is surprisingly 

 great, being about as large as the part of the tree above 

 ground. 



The wood of a tree is made up of concentric layers, which 

 on cross section appear as rings, called annual rings. The 

 age of a tree may approximately be told thereby. For the 

 origin of annual rings see page 307. The older heart wood 

 and the young sap wood generally show a difference of color, 

 the former usually being darker. The sap wood is still 

 active in carrying water, and storing sap, but the heart wood, 

 though containing moisture, does not enter any more into 



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