io6 
THE VEGETATIVE FUNCTIONS OF PLANTS 
observation justifies the inference that living plants 
take in oxygen. 
107. Carbon Dioxide Given Off. The air in each of 
the seven cylinders may next be tested with lime-water, 
by pouring in not more than 
one or two tablespoonfuls, and 
mixing it well with the air by 
tipping the cylinders, holding 
the halves with the plant ma- 
terial uppermost, and allowing 
the lime-water to flow back 
and forth a few times from one 
end of the jar to the other. 
Care should be taken not to 
dirty the lime-water by allow- 
ing it to rinse the plant mate- 
rial. After this treatment the 
lime-water will be found to 
have turned milky in all of the 
jars except the one containing 
no plant tissue. From these 
results we may correctly infer 
that carbon dioxide has been 
FIG. 69. A simple calorim- 
eter for studying the tempera- 
ture transformations in respira- 
tion. Respiring seeds are placed g i ven off by the plants. 
in the Dewar bulb (double walled, 
with a vacuum between the 
walls). At the bottom of the 
bulb is a dish containing caustic 
potash; cotton wool is packed 
between the thermometer and 
the neck of the bulb. (After 
Ganong.) 
108. Heat Evolved. That 
heat is evolved during the 
gaseous exchange above 
demonstrated may be illus- 
trated by placing a -delicate 
thermometer into, say, the germinating seeds. The best 
results will be obtained by placing the plant material into 
a double- walled Dewar flask (or a thermos bottle), which 
