96 
WORLD OF INVISIBLE LIFE 
What is a 
leaf li\e? 
Epidermis 
Stomas 
Section through 
a leaf 
instance. It is thin and green, with a ragged 
edge. There is a vein, or rib, down the center 
with smaller veins running out into the points. 
How different the same maple leaf looks under 
the microscope! 
We usually cut the leaf in two with a razor 
blade and take a thin crosswise slice to put 
under the microscope. We find that the leaf 
has a rather thick skin on its top and bottom. 
In the lower skin we see little slits or openings 
that look somewhat like mouths. They are the 
openings through which the plant breathes, and 
through which any extra water in the plant es¬ 
capes. They are rather like our pores through 
which we perspire in this respect, but they do 
the plant’s breathing besides. All plants have 
to breathe, for they cannot live without air any 
more than human beings can. The plant has 
no lungs, however, and the air passes into and 
out of the plant body through these openings. 
They are called stomas . The oxygen in the 
air is used up by the plant for its life processes 
and carbon dioxide given off, just as in humans. 
What is a 
leaf li\e? 
Epidermis 
Stomas 
Section through 
a leaf 
A maple leaf 
