30 



EXPERIMENTAL PLANT PHYSIOLOGY. 



fasten by means of rubber tubing a tube bent twice at right angles. 

 Insert the free end of the tube in a test-tube. The water thrown 

 out and through this tube by root-pressure will be collected in the 

 test-tube, and its volume can be compared with the amount drawn 

 out of the measuring-cylinder by the transpiration of the other part 

 of the plant (Fig. 25). 



Fig. 25. 



Comparison of root-pressure and transpiration. (After Oels.) 



