52 
MANUAL OF NATURE STUDY. 
planted on blotting paper, or on cotton in a tumb¬ 
ler of water. These may be seen, however, very 
well without a hand lens. 
Our next attention is to the leaf. Do roots and 
flowers have to do all the work there is to be done 
in the seed factory ? What are leaves for ? If a 
leaf, the under side of it, should be covered with 
dirt, what change in color would that part of the 
plant undergo? Did you ever see the corn-blades 
and maple leaves covered with dust from the road 
during dry time in August or September ? What 
effect did the dust have upon the thriftiness of the 
plants ? Did you ever wash the leaves of your 
house plants ? Why did you do so ? Could you 
breathe as well with your nostrils filled with dust ? 
The nostrils, or stomata of plants, are most 
numerous on the under side of the leaf. Do 
you now see why the leaves should be kept 
clean ? Does breathing air have anything to do 
with the growth of our bodies? How? Does 
breathing air and moisture have anything to do 
with the growth of the plant? Then does the leaf 
have anything to do in helping the flower to make 
seeds? 
Call attention to the many thousand mouths 
(stomata) of the leaf, and the fact that each little 
mouth is opened and shut at exactly the right time; 
