126 “ELEMENTARY BOTANY 
Take an empty jar I, and another jar IL, in 
which germinating seeds have been kept tightly 
corked for ee hours. Pour lime-water _ each jar 
and shake up. 
Experiment ii: 
The oe water does not change in I, but 
becomes milky in II. 
There is little or no carbon dioxide in I. and 
enough in Il. to be tested, therefore carbon 
dioxide has been given out by the germinating seeds. 
Result. 
Conclusion. 
Put some ger- 
minating seeds 
into a jar, and also a. test- 
tube containing caustic potash. 
Cork the jar with an india-— 
rubber cork, into which has 
been fitted a bent tube with 
coloured liquid. 
The volume of 
air in the jar gets 
less, and the liquid gradually 
rises along the bent arm of 
the tube. 
Experiment III. 
Result. 
As caustic 
potash is known 
Fie. 143.—APPARATUS TO SHOW to absorb carbon dioxide, the 
THAT PLANTS TAKE IN volume of air in the jar is 
OXYGEN. 
being diminished by the amount 
of oxygen taken in by the seeds, and the liquid rises in the 
bent tube to replace the oxygen. 
This experiment is more satisfactory than Experiment I., for 
in this case the carbon dioxide being absorbed by the caustic 
potash, the only change going on in the air of the jar is the 
withdrawal of oxygen. These experiments show clearly that 
plants take in oxygen from the air and give out carbon dioxide. 
Take some germinating barley seeds and 
also some barley seeds which have been killed 
by boiling. Place them respectively in two vessels surrounding 

Conclusion. 

Experiment IV. 
