UNDER THE MAPLES 



the fact that its cambium layer, at least over a part 

 of its surface, is still youthful and doing its work. 

 It is this layer that the yellow-bellied woodpecker, 

 known as the sapsucker, drills into and devours, 

 thus drawing directly upon the vitality of the tree. 

 But his ravages are rarely serious. Only in two 

 instances have I seen dead branches on an apple- 

 tree that appeared to be the result of his drilling. 

 What we call the heart of a tree is in no sense 

 the heart; it has no vital function, but only the 

 mechanical one of strength and support. It adds 

 to the tree's inertia and power to resist storms. 

 The trunk of a tree is like a community where only 

 one generation at a time is engaged in active busi- 

 ness, the great mass of the population being retired 

 and adding solidity and permanence to the social 

 organism. The rootlets of a plant or a tree are 

 like the laborers in the field that produce for us 

 the raw material of our food, while the leaves are 

 like our many devices for rendering it edible and 

 nourishing. The rootlets continue their activity 

 in the fall, after the leaves have fallen, and 

 thus gorge the tree with fluid against the needs of 

 the spring. In the growing tree or vine the sap, 

 charged with nourishment, flows down from the 

 top to the roots. In the spring it evidently 

 flows upward, seeking the air through the leaves. 

 Or rather, we may say that the crude sap always 

 flows upward, while the nutritive sap flows down- 



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