170 LEAVES 



154. LEAVES 



Object. To study the fall of a leaf. 



Apparatus. Any healthy deciduous plant such as maple, ash, 

 ailanthus, hickory, or horse-chestnut, a large black cloth or a dark 

 box. 



Method. Cover the leaves of one branch or cover one 

 leaf with the cloth, haying first dampened it, or place the 

 leaf in a dark box and stop up the aperture so as to shut 

 out light. Let the apparatus remain for at least a week, 

 then remove the coverings and note the result. 



Note. The leaf will usually drop off and its leaf scar on the 

 stem will be found as in autumn. 



Conclusion. How may this be explained ? 

 Query. Why do leaves on a tree, where they are over- 

 shaded, turn yellow and fall during the summer ? 



Food Storage in Leaves 



It has been shown that green leaves manufacture foods. 

 In some plants the various food products are transferred to 

 other parts of the plant and stored there. The fleshy roots 

 and stems have been shown to be storage places for food. 



In some plants the leaf is also used to store food. 



In the foregoing experiments we have found starch in the 

 leaves after exposure to sunlight. 



Suggestion. Test leaves of lettuce, spinach, cabbage, 

 celery, etc., for starch by first soaking in alcohol to remove 

 the chlorophyll and then look for blue color after treating 

 with iodine solution. For sugar macerate the leaves in 

 water, filter, and test for sugar. 



For oils and fats dry the leaves and treat them with 

 alcanna solution or with Soudan III. 



