o2 A TEXTBOOK OF GENERAL BOTANY 
given off by the seeds is absorbed by the solution, so that as 
oxygen is taken up the solution rises in the tube. This experi- 
ment can be checked by placing germinating seeds in another 
tube and inverting the tube over mercury, which does not absorb 
carbon dioxide. The mercury will not rise in the tube, because 
the oxygen that is taken up by the seeds is replaced by carbon 
dioxide, and, as the latter is not absorbed by 
the mercury, the volume of gas is not de- 
creased. A green leaf can be used in place of 
the seeds in this demonstration if the prep- 
aration is kept in the dark. 
Heat is produced by respiration. This can 
be demonstrated by the arrangement shown in 
Fig. 39. A vacuum flask is partially filled with 
germinating seeds. A vial containing potas- 
sium hydroxide is also placed in the flask to 
absorb carbon dioxide. A thermometer is then 
inserted through the mouth so that the bulb is 
among the seeds. The mouth is now plugged 
with cotton, which allows air to enter the flask. 
The heat produced by respiration causes the 
mercury to rise in the thermometer. This ex- 
periment should be checked by setting up a 
Fic. 39. Apparatus preparation similar to the one just described 
for demonstrating except that the germinating seeds are replaced 
liberation of heat : 
meee raron by dead ones. In the latter case the thermom- 
eter will not show a rise in temperature. 
Respiration in plants and animals. Respiration is fundamen- 
tally the same process in both plants and animals, and consists 
essentially in the liberation of energy by the oxidation of com- 
pounds containing carbon and hydrogen. The methods by which 
oxygen enters the body and carbon dioxide leaves it are very 
different in the higher groups of the two kingdoms. These 
processes, however, are only incidental to the fundamental one 
of oxidation. Also, the methods by which the materials to be 
oxidized are obtained are very different in green plants and in 


