Instinct-like Work. 57 



growth build up the trunk and all the machinery 

 of the roots for the benefit of the thousands of in- 

 dividual plants or buds that make a full grown 

 tree. In the same way, but under the impulse and 

 guidance of Instinct, do social animals, like the hor- 

 net and beaver, build nests and dams for the com- 

 mon good. 



Since the tree is fixed to one place and yet must 

 feed mainly upon the products of the soil, it pro- 

 vides for itself anew every year organs for feeding, 

 by increasing its surface of root by the formation 

 of fibrils that penetrate the soil in all directions. 

 The food of the tree consists of the salts and gases 

 in solution. As these substances are carried down 

 by abundant surface rains, or drawn up by capilla- 

 ry attraction, they cannot escape the eager rootlets 

 that sweep the soil in all directions by their fixed 

 net-work, as completely as the coral polyp and oth- 

 er forms of animals sweep the waters with their ten- 

 tacles. 



In the spring time also the tree puts out its 

 wealth of leaves to gather additional food from the 

 air. And what ample provision is made for carry- 

 ing on this work ! What apparent forethought and 

 wisdom do we here find in the economy of the tree ! 

 The leaf not only gathers crude materials from the 

 air, but it is the laboratory in which all materials 

 taken from both earth and air are elaborated and 

 fitted for building up the tree in all its parts. The 

 material that forms the leaf must itself be first elab- 

 orated. How shall the tree without leaves clothe 

 itself with its acres of foliage ? It does this by a fore- 



