THE LIBERATION OF ENERGY IN PLANTS 65 



twenty-four hours. Rinse the seeds with boiled water to 

 remove the preserving fluid. Get two thermometers that 

 have approximately the same temperature reading in the air 

 of the laboratory. 1 Push the lower end of the thermometer 

 down among the sprouting seeds so that the mercury will be 

 covered by the seeds. Do the same with the second ther- 

 mometer in the jar of dead seeds. Set the jars side by side 

 in a warm place for twenty-four hours or more. 



1. Describe the preparation of this experiment. In what 



respects are the conditions the same in both jars? In 

 what one respect do the two jars differ? 



2. Take the temperature readings of the thermometer in each 



of the two jars and record results. What difference 

 do you notice in the temperature of the seeds in the two 

 jars? 



3. What is your conclusion from the experiment as to the 



liberation of heat energy in seedlings ? 



76. Energy and its transformations. We see from the 

 preceding discussion and experiment that plants exhibit 

 considerable energy or ability to do work. Animals and 

 man, however, show far more striking proofs of the output of 

 energy in their muscular movements, for example, in running, 

 swimming, and flying. Various machines, also, enable us to 

 make use of different forms of energy, and, as we shall now 

 see, one kind of energy may be readily transformed into 

 another by means of these machines. Suppose we consider 

 the work that goes on in an electric power plant. The coal 

 that is shoveled into the fire-box beneath the boilers by the 

 process of oxidation liberates heat, which is one of the forms 

 of energy. The heat changes the water .into steam, which 

 expands and so exerts its power to run the engine, and thus 

 heat energy is transformed into the energy of motion. When 

 the engine is connected with a dynamo, this energy of mo- 



1 If a difference in the reading of the two thermometers is evident, 

 this difference should be computed in the later readings on the ther- 

 mometers. 



