HOW THE LEAF GETS FOOD FROM THE AIR 75 



39. Fill a bottle full of water and force the stopper as 



far down into it as you can. Placing a string or piece 



of fine wire between the cork and the glass aids this, 



as the water follows the string when it is drawn out. 



Take care that there is no air in the bottle. Now pull 



gently on the stopper, twisting 



it at the same time. Or hang 



up the bottle in sunlight as 



shown in the figure. The air 



which enters the leaves will be 



seen coming out of the end of 



the stem. Why? Magnolia 



and cherry laurel are good for 



this experiment. We may now 



ask the question : * 



How does the air enter the 

 leaf: are there openings for this 

 purpose? Put some leaves in 

 cold water and remove any air 

 bubbles that cling to them by 

 rubbing them under water. 

 Bring some water to a boil, take 

 it off the stove, and at once 

 plunge the leaves into it. If there are openings, air 

 will come out of them and show where they are. 

 (Leaves of laurustinus, Christmas berry, cherry laurel, 

 and geranium are good for this experiment.) 



These openings are called stomata or breathing pores. 



FIG. 39. A branch fitted 

 into a cork which stop- 

 pers a bottle of water. 

 As the branch draws 

 water out of the bottle air 

 is drawn in through the 

 leaves, and bubbles up 

 from the end of the stem. 



