WATER FOR THE PLANT 



the leaves as vapor. As soon as the air under the glass receives more 

 moisture than it can hold in the form of a vapor or gas, the extra mois- 

 ture gathers in drops on the inside of the glass. 



How plants lift water. What force enables plants to 

 collect water from the ground and lift it into the roots and 

 stems ? To understand this, we need to study the tiny parts 

 or cells of which the plant consists. We may think of a 

 plant cell as a tiny room, too small 

 even to be seen without a powerful 

 microscope. But this little room or 

 cell has no doors nor windows nor 

 other openings into it. It is com- 

 pletely lined on the inside with a 

 layer of living jelly-like material. 

 This layer lets water and the material 

 dissolved in water soak through it 

 and thus pass to the inside of the 



cell. An important fact to remem- 



. . FIG. 26. SHOWING THAT 



ber is that the water passes in, but WATER is THROWN OFF 



will not pass out into the soil again FROM THE LEAVES OF 



GROWING PLANTS 

 while the plant is healthy. This is 



partly because the water in the soil is more dilute than 

 the sap which fills the plant cell; and also because the 

 dilute soil water can flow in through the cell lining more 

 rapidly than the denser sap inside can flow out into 

 the soil. This flow of water towards the sap or denser 

 liquid helps to force water upward from the roots. The 

 leaves assist in the upward flow, for water must rise 

 to take the place of that which the leaves give off into 

 the air. 



