THE LIFE OF A PRIMROSE. ^5 
into food to be sent to all parts of its body. In this 
way these leaves act, you see, as the stomach of the 
plant, and digest its food. 
Sometimes more water is drawn up into the leaves 
than can be used, and then the leaf opens thousands 
of little mouths in the skin of its under surface, which 
let the drops out just as drops of perspiration ooze 
through our skin when we are overheated. These 
little mouths, which are called stomates (a, Fig. 44), 
are made of two flattened cells, fit- 
ting against each other. When the 
air is damp and the plant has too 
much water these lie open and let it 
out, but when the air is dry, and 
the plant wants to keep as much 
water as it can, then they are closely 
shut. There are as many as a hun- FlG - 
dred thousand of these mouths 
under one apple-leaf, so you may imagine how small 
they often are. 
Plants which only live one year, such as migno- 
nette, the sweet pea, and the poppy, take in just enough 
food to supply their daily wants and to make the seeds 
we shall speak of presently. Then, as soon as their 
seeds are ripe their roots begin to shrivel, and water 
is no longer carried up. The green cells can no longer 
get food to digest, and they themselves are broken 
up by the sunbeams and turn yellow, and the plant dies. 
But many plants are more industrious than the 
sweet pea and mignonette, and lay by store for another 
year, and our primrose is one of these. Look at this 
thick solid mass below the primrose leaves, out of 
