THE WATER-RELATION 97 



from their encysted structure that the nutrition of plants must be 

 solely by substances in solution. The ultimate importance for plants 

 of the water-relation lies then in nutrition. For water is the medium 

 of presentation of the soluble nutriment, which can thus pass through 

 the cell-wall to the active protoplast within. It is in the protoplasts 

 that the plant is able to build up its own organic compounds, using 

 lor that purpose the substances- thus acquired. 



B.I3. 



