ROOT AND CKOWN. 71 



processes may be carried on. This water will not 

 be chemically bound, like that which is used in 

 food, and will not long be retained. We must con- 

 ceive that water is continually streaming through 

 the living plant. In the course of a summer, an 

 amount of water passes through the plant which 

 many times exceeds its weight. The water which 

 is chemically united with the organic compounds 

 of the plant, is extremely slight in comparison 

 with that used in carrying its food materials. . . . 

 It is therefore plain, as water is a necessary 

 food, and is needful in transporting other food 

 materials, that a sufficient supply is indispensable 

 to the life of the plant. 1 



1 " Pflanzenleben," I. pp. 199, 200. 



