PERSONALITY OF PLANTS 
graphically demonstrated by placing a plant 
in a glass jar of carbon dioxide inverted in 
water. If its life processes are quickened by 
exposure to sunlight, the plant will replace the 
COz with oxygen in a day. A more striking 
example is furnished by any aquatic plant ac- 
customed to growing submerged in ponds and 
rivers. Placed in a water-filled bottle inverted 
in a pan of water, it will generate oxygen so 
rapidly that the bubbles can be seen forming 
on the leaves when the sun is allowed to strike 
them fully. The bottle will become filled with 
oxygen in a few hours, and its presence can be 
demonstrated with the usual ember test. 
Opposed to the absorption of carbon dioxide 
and the breathing out of oxygen, which is really 
a digestive operation, the plants, queerly 
enough, carry on a directly opposite process 
which involves the absorption of oxygen and 
the breathing out of carbon dioxide. This is 
a respiratory process akin to breathing in ani- 
mals. It is carried on in such a relatively small 
way that it does not seriously affect the state- 
ment that “plants breathe in carbon dioxide 
and breathe out oxygen” and so are purifiers 
[134] 
