ASCENDING SAP 111 



quantity of water and a very small proportion of 

 dissolved substances. These inconsiderable sub- 

 stances are the only or almost the only things utilized 

 by the plant ; and the water that has collected them 

 in filtering through the soil, and has then carried 

 them from the roots to the leaves through the sap- 

 wood, the water that forms almost the whole of the 

 ascending sap, is destined, as soon as the journey is 

 accomplished, to leave the plant and return as vapor 

 to the atmosphere whence it descended in the form 

 of rain." 



