10 ESSENTIALS OF BOTANY 



instance peas, in a room at the ordinary temperature, the 

 peas will be found to be warmer than the surrounding 

 air. This rise of temperature is at least partly due to 

 the absorption from the air of that substance in it which 

 supports the life of animals and maintains the burning 

 of fires, namely, oxygen. 



The union of oxygen with substances with which it 

 can combine, that is with those which will burn, is called 

 oxidation. This kind of chemical change is universal in 

 plants and animals while they are in an active condition, 

 and the energy which they manifest in their growth and 

 movements is as directly the result of the oxidation going 

 on inside them as the energy of a steam engine is the 

 result of the burning of coal or other fuel under its boiler. 

 In the sprouting seed much of the energy produced by the 

 action of oxygeii upon oxidizable portions of its contents 

 is expended in producing growth, but some of this energy 

 is wasted by being transformed into heat which escapes 

 into the surrounding soil. It is this escaping heat which 

 is detected by a thermometer thrust into a quantity of 

 germinating seeds. 



EXPERIJIENT III 



Effect of Germinating Seeds upon the Surrounding Air. — When 

 Exp. II has been finished, remove a little of the air from above the 

 peas in the first bottle. This can easily be done with a rubber bulb 

 attached to a short glass tube. Then bubble this air through some 

 clear, filtered limewater. Also blow the breath through some lime- 

 water by aid of a short glass tube. Explain any similarity in 

 results obtained. (Carbon dioxide turns limewater milky.) After- 

 wards insert into the air above the peas in the same bottle a lighted 

 pine splinter, and note the effect upon its flame. 



