22 



EXPERIMENTAL PLANT PHYSIOLOGY. 



17. Water Evaporates from Leaves as from a Membrane. The 



shoots and leaves of plants give off water in a manner similar 

 to the action of the apparatus in the above experiments. 

 EXPERIMENT 26. 



LIFTING-POWER OF TRANSPIRATION. 



By means of a closely-fitting rubber stopper fasten a leafy shoot 

 of a woody plant (Raspberry, Rosebush, etc;) in one end of a U tube 

 filled with water and FIG. 19. 



mercury. The mercury 

 in the open arm of the 

 tube soon begins to sink, 

 indicating a loss of water 

 from the leaves. (Fig. 

 1 8.) This fact may alsc 

 be demonstrated by fit- 

 ting the shoot to the 

 upper end of a straight 

 tube whose lower end is 



FIG. 18. 



Lifting power of transpira- 

 tion. (After Oels.) a, 

 water; b, mercury. 



Lifting power of transpiration. 

 (Detmer.) 



