38 HORTICULTURE FOR SCHOOLS 



Procedure. Put a small amount of water into a quart jar having 

 a tight cover. Fill the jar half full of the leaves. Set a vial of lime- 

 water in the jar. Fasten the cover and put the jar in a dark place for 

 twenty-four hours. A scum on the surface of the lime-water indicates 

 the presence of carbon dioxide. What process was stopped by putting 

 the jar in the dark? 



EXERCISE XI. Experiment with chlorophyll. 



Materials. Test-tubes; \vater; alcohol; benzol; corks; leaves. 



Procedure. Place a leaf in a little water in a test-tube and boil. 

 Pour in alcohol, and heat. The solution appears green and contains 

 chlorophyll and other colored substances. To separate these pour 

 in a little benzol. Shake thoroughly. Place a cork in the tube and let 

 stand. The bluish green substance is chlorophyll; the other substances 

 are yellow. 



EXERCISE XII. Exercise to show the presence of starch in leaves. 



Materials. Alcohol; leaves; tincture of iodine. 



Procedure. Extract the chlorophyll from a leaf with alcohol as in 

 the preceding exercise. Mash the leaf from which the chlorophyll has 

 been removed, and add to it a few drops of dilute tincture of iodine. 

 A blue color indicates the presence of starch. 



