CH. Ill] 



EXUDATION OF WATER. 



77 



pressure tube which is also tied to the plant \ The arm B 

 passes through a rubber cork firmly tied into a wide- 



Fig. 14. Exp. 89 A. 



mouthed (stoppered) bottle, in the bottom of which is half 

 an inch of mercury, Hg: the tube M, which serves for 

 manometer readings, fits tightly into a hole in the cork 

 and reaches the bottom of the bottle. Water W is now 

 poured in at C so that the bottle and the arm T are filled. 

 At first the plant will usually absorb water, so that C 

 should be left open until the rise begins, when it may be 

 filled up and closed by means of a clamp. The mercury 

 will rise to a considerable height and will show diurnal 

 variations about its mean position. 



(90) Moll's Experiment. 



Various kinds of plants, when placed under a bell- 



jar standing in dishes of water, will give evidence of root 



1 The two ligatures at T are placed closer together than as repre- 

 sented in fig. 14. 



