LEAVES 167 



the relation of light to green coloring matter (chlorophyll) 

 in plants, also the relation of these to starch making. 



Suggestion. Repeat this experiment, using a leaf picked 

 from the plant early in the morning before the sun has 

 shone upon it. Does the leaf give the same starch tests? 

 How do you account for the difference ? 



Note. The color of green plants is due to the presence of small 

 green grains called chloroplasts. They may be seen with a low power 

 of the microscope if thin sections of leaves be examined in a drop 

 of water or glycerin. These small bodies have the power of making 

 starch out of water and carbon dioxide in the presence of sunlight. 

 In this process, called photosynthesis, oxygen is set free. 



The leaf is a sort of factory in which water and carbon dioxide 

 are the raw materials, the chloroplasts are the machinery, sunlight 

 is the energy, starch and other substances are the finished product, 

 and oxygen is the waste product. 



Only green plants are capable of making starch. 



150. LEAVES 



Object. To prove that it is only in the green part that 

 starch is made. 



Apparatus. Spotted leaves of such plants as silver-leaf gera- 

 nium and some varieties of coleus, also &ny dicotyl albino plants, 

 and the same tests as used in the preceding Experiment. 



Method. Treat the leaves as in the foregoing Experiment 

 by boiling the leaves for a few minutes in water, then soak- 

 ing them in alcohol and adding iodine solution. Which part 

 of the leaf turns blue ? Inference ? 



Conclusion. State what kind of plants and what parts 

 of plants are engaged in starch making. 



Suggestion. Test mushrooms and other fungi, also red 

 or yellow plants like dodder, in the same way. 



