CHAPTER XVII 
THE KIND OF GAS WHICH PLANTS GIVE OFF WHILE 
MAKING STARCH 
How to catch this gas in a tube. 
We are interested 
to learn more of this gas, and to know, if possible, 
what it is. We can catch some 
of it in a tube in the following 
way. We will take the elodea 
or some other suitable water 
plant. Place it in a tall, wide 
jar and invert a funnel over it 
so that the small end of the 
funnel will be under the surface 
of the water. Sink a test tube 
in the water, and then, without 
bringing the open end of the 
tube out of the water, invert it 
and lower it over the end of the 
funnel as shown in Fig. 153. Set 
the jar in the sunlight and leave 
it there for several days, arrang- 
ing something to hold down 

Fic. 153. Catching the bubbles 
of gas in a test tube. 
the tube in case it becomes full of the buoyant gas. 
121 
