68 PLANT BIOLOGY 



of a plant is in some way set free by oxygen acting upon 

 plant compounds. When oxidation of compounds containing 

 carbon takes place, we find that carbon dioxid is produced 

 (11). Now if processes like oxidation are carried on in plants, 

 we should expect to find that CO2 is formed. The following 

 experiment proves clearly that such is the case. 



81. To prove that carbon dioxid is formed during the 

 growth of young seedlings. Laboratory Study No. 40. 



In the bottom of two large jars (fruit jars will answer) 

 place some wet blotting paper. Fill one of the jars half full of 

 germinating peas, and place a small wide-mouthed bottle 

 full of lime water on top of the seeds. Screw the top of the 

 jar on tightly. In the other jar place a bottle of lime water 

 and cover as in the previous jar. At the end of twenty-four 

 hours or more examine the lime water in both jars. 



1. Describe the preparation of the experiment. 



2. Compare the condition of the lime water in both jars. 



What has caused the change in the lime water in both 

 jars? 



3. Air, as we proved, contains a little carbon dioxid. Bearing 



this fact in mind, account for the difference in the ap- 

 pearance of the lime water in the two jars. 



4. What gas, therefore, do you find to be given off during 



the growth of young seedlings ? 



II. RESPIRATION 



82. Respiration in plants. It should be clear from our 

 study thus far that all plants require oxygen, and that this 

 oxygen brings about in plants a process resembling oxidation 

 at least in the releasing of heat and other forms of energy 

 and in the producing of carbon dioxid. These various pro- 

 cesses take place in each living plant cell. Hence, every 

 cell uses oxygen and must necessarily form carbon dioxid. 

 This process which goes on in every living cell is respiration. 



