158 LEAVES 



Method. Dry the leaves thoroughly and burn them. 

 Which leaves contain the greater amount of ash? Account 

 for this. 



Conclusion. State whether young or old leaves contain 

 more mineral substance. 



Note. Compare the crust of lime left in a teakettle with the 

 mineral left in a leaf. What corresponds to the steam that comes 

 from the kettle ? Trace a drop of water from the soil through a 

 plant until it returns to the atmosphere. 



How do you account for the presence of potash in wood ashes ? 



139. LEAVES 



Object. To find tlw cause of wilting and recovery. 



Apparatus. Leaves of hydrangea or other similar plant, 

 tumbler, and water. 



Method. Cut off a leaf and let it lie upon the table in 

 the sunlight until it is wilted. Then place the leafstalk 

 in water. What happens? Repeat the experiment, put- 

 ting only the blade in water. Does it recover ? 



Conclusion. What causes a leaf to wilt ? What causes 

 it to recover? How does water get into the leaf? Where 

 does it go out? 



140. LEAVES 



Object. To find out which surface of a leaf gives off 

 most water- 



Apparatus. Four leaves of hydrangea or other plant of similar 

 kind which wilts easily, vaseline, or olive oil. 



Method. Suspend the four leaves by threads so that all 

 surfaces will be equally exposed to the air. 

 No. 1. Leaves in natural state. 

 No. 2. Coat upper surface with vaseline. 



