NATUBE-STUBY LESSONS. 119 



19. (a) Place in this jar, containing a little water and 



the product of the "burned candle, a few 

 sprays of mint or other green plant. Seal 

 it and set it aside for two or three days in 

 the sunlight. Then test the gas within the 

 jar by lighting a candle and placing it in 

 the jar. 

 (S) What is the result ?* 



(c) Is the gas in the jar the same now as that in 



the jar when it was set away ? 



(d) Account for the result you observe. 



20. While awaiting the results of the above experi- 

 ment, take another bottle or jar and place a little lime- 

 water in the bottom. Burn a candle within the bottle 

 until it will burn no longer. Now, shake the bottle vig- 

 orously, holding the hand over the mouth of the bottle. 



21. Examine the lime-water. 



22. What changes have you observed ? 



The gas which enables the candle to burn is oxygen. Oxygen is pro- 

 duced, and carbon dioxide is assimilated, in the little cells of the leaf 

 through the action of small green bodies in the cells, which give the green 

 color to the leaf. 



23. From these experiments, what do you infer to be 

 one of the foods of the plant taken in by the leaf.? 



24. What gas in the process of food-digestion is given 

 off into the air ? 



25. {a) By means of a straw or glass tube, cause the 



air from your lungs to bubble through some 

 lime-water in a glass. Continue the bub- 

 bling for some time. Then examine the 

 lime-water. 

 (p) What change has taken place ? 



