146 
Now, even wise men have to do some guessing 
about this matter, and I fear you will find it a little 
hard to understand. 
But it is believed that the roots drink in the earth 
broth so eagerly and so quickly, that before they know 
it they are full to overflowing. It is easier, however, 
to enter a root than it is to leave it by the same door; 
and the result is, that the broth is forced upward into 
the stem by the pressure of more water or broth behind. 
Of course, if the stem and branches and leaves 
above are already full of liquid, unless they have some 
way of disposing of the supply on hand, they cannot 
take in any more; and the roots below would then be 
forced to stop drinking, for when a thing is already 
quite full to overflowing, it cannot be made to hold 
more. 
But leaves have a habit of getting rid of what they do 
not need. When the watery broth is cooked in the sun, 
the heat of the sun’s rays causes the water 
ae to pass off through the little leaf mouths. 
\ Thus the broth is made fit for plant food, 
and at the same time room is provided for 
fresh supplies from the root. 
ae If you should examine the lower side of 
a leaf through a microscope, you would 
ag 38) find hundreds and thousands of tiny 
mouths, looking like the little mouths in this picture 
Cig 2637). 
Some of the water from the earth broth is constantly 
passing through these mouths out of the plant, into 
the air. 
