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the cork in the lower end of the tube A, and its upper end is 

 drawn into a capillary tube to regulate the rate of inflow of 

 air as water passes from the tube A, into bottle B, as the 

 plant roots absorb the water from the bottle. It is necessary 

 to have the bottle B, and tubes S and A filled with water at 

 the beginning of the experiment, and then, with a pipette, 

 draw off water from the bottle until a bubble of air passes 

 from tube T into tube A. Now, as the plant takes up water by 

 means of its roots and the surface of the water in B sinks 

 below a level with the lower end of T, water will flow from A 

 into B through S and air will pass through the capillary end 

 of T and rise from the lower end of T in single bubbles and 

 at regular intervals - the time between bubbles depending alone 

 on the rapidity of absorption of water by the roots of the 

 plant. The tube A has a scale, graduated to half cubic centi- 

 meters etched on its surface by means of which readings can 

 be made. 



By means of this piece of apparatus the same constant 

 level of water is maintained in the vessel containing the 

 plants. The evaporation from the surface of the water through 

 the opening is reduced to a minimum by stopping the opening 

 around the stem of the plant with cotton. 



It was intended that considerable work would be done with 

 the use of this apparatus on the absorption of water by the 



