THE RELATION OF THE PLANT TO THE AIR 127 
two thermometers. The vessels must stand in a dish con- 
taining caustic potash, so that the carbon dioxide given out 
by the germinating seeds may be absorbed. Cover with a 
bell-jar. (See Fig. 144.) 
The thermometer in the vessel with the germi- 
nating seeds is 2° above that in the other vessel. 
Conclusion. Heat is given out in breathing. 
Take some germinating seeds which have 
been kept in bottles an the dark for a day, and 
repeat Experiments I. and II. 
The same as be- 
fore. : 
Respiration goes 
on in the dark. — 
The above experiments show 
that during respiration, plants 
are taking in oxygen and 
giving out carbon dioxide; 
that respiration therefore can- 
not take place to any great 
extent without oxygen; that 
during respiration heat 1s pro- 
duced, and that it goes on in 
the dark as well as in the 
light. . 
We have already seen that Fic. 144, — APPARATUS TO SHOW 
THAT PLANTS GIVE OUT HEAT 
a plant consists of cells, and IN RESPIRATION. 
that each cell consists of proto- 
plasm. We must now picture all the cells of a plant breath- - 
ing, and during this process taking in oxygen, which is 
necessary for them if they are to keep well and able to do 
their work, and at the same time giving out carbon dioxide, 
produced by the decomposition of the cell protoplasm. The 
respiration of plants, therefore, is similar to that of animals. 
If animals are shut up with an insufficient supply of air, after 
a time they cease to breathe, and die, as in the Black Hole of 
Calcutta, owing to the absence of oxygen. 
Result. 
Experiment V. 
Result. 
Conclusion. 

