WORK OF LEAVES: PHOTOSYNTHESIS 



107 



splinter is inserted in the mouth of the tube. It flames again. 

 This indicates that the gas is oxygen. 



170. To show that carbon dioxide is absorbed while 

 oxygen is given off by plants. Boil some spring water. This 

 drives off the air and carbon dioxide which is mixed in it. When 

 the water is cooled a few sprigs of Elodea are placed in it as 

 described in paragraph 168. It is now placed in the sunlight. 

 No gas is given off. If oxygen is added by thoroughly agitating 



Fig. 89. 

 Ready to see what the gas is. 



the water so as to mix air with it, and it is placed in the sunlight, 

 no gas is given off. If carbon dioxide is now added (by breathing 

 into the water through a glass tube, or with a gas generator), 

 and it is placed in the sunlight, oxygen is again given off. 



171. A chemical change takes place in the gas in the cells 

 of the plant.* These experiments indicate that a chemical 

 * For reference. 



