CH. Ill] 



EXUDATION OF WATER. 



77 



pressure tube which is also tied to the plant 1 . 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, 

 and C is closed with a clamp. H. S. Chamberlain's book, 

 Lei Seve Ascendante (Neuchatel, 1897), contains descrip- 

 tions of new apparatus for observing root-pressure. See 

 also his curious observations on the effects, on root-force, 

 of increased and diminished pressure. 



(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 thaii as repre- 

 sented in fig. 14. 



