60 LABORATORY AND FIELD EXERCISES 



three jars (1) before the candles are placed in them, 

 (2) immediately after the candles cease to burn, 

 and (3) at the close of the experiment, before the 

 corks are removed. Explain also the daily gaseous 

 income and outgo of the exposed and the covered 

 plants in the two jars during the period of the 

 experiment. How and why would they differ in 

 this respect? 



e. Considering the results of the above experiment, how 

 do plants affect the air of a living room by day ? at 

 night ? Is it healthful to have a large number of plants 

 in a living room? Give reasons for your conclusions 

 concerning this matter. 



B. RESPIRATION 



1. Gaseous exchange of plant parts during respiration. Indi- 

 vidual experiment. 



a. Select two bottles or pint fruit jars with wide mouths. 



Put into one bottle or jar enough dry peas or beans 

 to cover the bottom. In the second receptacle place 

 a similar amount of germinating seeds after they have 

 been sterilized in a weak formalin solution. Test the 

 air in each receptacle with a burning match to see if 

 it supports combustion. Cork air-tight and set aside 

 for twenty-four or forty-eight hours. 



b. After the above period remove the corks and test the 



air again with a lighted match. Result ? 



c. Write up the experiment, indicating the composition of 



the air in the receptacles at the beginning and 

 at the end of the experiment. Indicate also the gase- 

 ous income and outgo of the seeds in each jar during 

 the time of the experiment. 



