THE PLANT AND WATER 201 



We also learned in a former lesson that the most im- 

 portant plant foods are: Water, lime, iron oxide, soda, 

 ammonia, silicon, magnesia, potash, carbon dioxide, phos- 

 phoric acid, etc. 



Water as a plant food and solvent. Perhaps the 

 most important plant food is water. Every one knows 

 that plants cannot live without water, but few persons 

 stop to think of the enormous amount of water consumed 

 daily by an acre of growing vegetation. Plants make 

 use of water in two ways. In the first place they use 

 it as a food, just the same as animals do. In the sec- 

 ond place a plant cannot eat solid food. It has neither 

 mouth nor teeth, and it must take in its food in liquid 

 form through its roots, or in gaseous form through its 

 leaves. The solid foods mentioned above dissolve in wa- 

 ter, just as sugar dissolves in coffee, and in this dissolved 

 condition they are easily taken in by the plant roots. 

 The plant fluid containing these dissolved foods is called 

 sap. The solid food and some of the water taken up 

 by the plant roots and carried through the stem to the 

 leaves is used by the plant for growth, and the re- 

 maining water not used for food is thrown off into the 

 air through little pores in the leaves. This is she rea- 

 son why plants need so much water. Grains, grasses, 

 and orchards use up hundreds of tons of water during 

 the growing season. 



Control of water for plants. We have also learned 

 that the farmer can regulate the amount of water in 

 the soil to a certain extent. If there is too much water, 



