HOW WATER MOTES THROUGH THE PLANT. 53 



water on the surfaces of the leaves, or at the cut ends, before it may have 

 condensed there, we infer that the water escapes from the leaves in the form 

 of water vapor, and that this water vapor, when it comes in contact with tha 



Fig. 45- Fig- 46. 



Leaves removed to show drops of water Photographed after the water has been 



on inside of jar. wiped from inside of jar. 



surface of the cold glass, condenses and forms the moisture film, and later 

 the drops of water. The leaves of these cut shoots therefore lose water in 

 the form of water vapor, and thus a loss of turgidity results. 



Demonstration 1 8. 



96. Loss of water from growing plants. Suppose we now take a small 

 and actively growing plant in a pot, and cover the pot and the soil with a 

 sheet of rubber cloth which fits tightly around the stem of the plant (or the 

 pot and soil may be enclosed in a hermetically sealed vessel) so that 

 the moisture from the soil cannot escape. Then place a bell jar over the 

 plant, and set in a brightly lighted place, at a temperature suitable for 

 growth. In the course of a few minutes on a dry day a moisture film forms 

 on the inner surface of the glass, just as it did in the case of the glass jar 

 containing the cut shoots and leaves. Later the moisture has condensed so 

 that it is in the form of drops. If we have the same leaf surface here as we 

 had with the cut shoots, we will probably find that a larger amount of 

 water accumulates on the surface of the jar from the plant that is still at- 

 tached to its roots. 



97. Water escapes from the surfaces of living leaves in the 

 form of water vapor. This living plant then has lost water, 

 which also escapes in the form of water vapor. Since here there 



