10 THE FOOD OF PLANTS CHAP, i 



upper surface en the metal surface. Very little water 

 will now be found on the metal, showing that most 

 of the water-vapour is escaping from the under surface 

 of the leaf. 



In order to find out why the water escapes from 

 the under surface more than from the upper surface, 

 you must examine the leaf under a microscope, so as 

 to magnify it. We then see that the under surface 

 is covered with tiny little openings or mouths called 

 stomata, from which the water-vapour escapes. 



These stomata, however, have something else to 

 do as well as to breathe out water -vapour, as we 

 shall find out later on. 



We now know that water is sucked in by 

 the roots, passes up the stem, and into the 

 leaves, and then passes off from the leaves as 

 water- vapour ; and that in this way the plant 

 gets what drink it needs to keep it alive and 

 growing. 



