Conditions and Principles of Absorption 83 



species of plants (see section 49). In determining the amount 

 of exudation, conduct in each case the liquid into a graduated 

 test-tube with foot, in which test-tube is placed a drop or two 

 of oil to prevent evaporation. In the pressure determination 

 employ a Ganong manometer, or one similar in principle im- 

 provised from materials at hand. Observe frequently, calculate 

 the pressures at the different intervals, and draw curve of 

 results. 



REFERENCES 



ECKERSON, S. H. Root Pressure and Exudation. Bot. Gaz. 45 : 



50-54, 1908. 

 KAHLENBERG, L. On the Nature of the Process of Osmosis and 



Osmotic Pressure. Journ. Phys. Chem. 10 : 141-209, 1906. 

 LIVINGSTON, B. E. The Role of Diffusion and Osmotic Pressure 



in Plants. Dec. Publ. Univ. Chicago. 8 : 149 pp., 1903. 

 NATHANSOHN, A. Ueber die Regulation der Aufnahme anor- 



ganische Salze durch die Knollen von Dahlia. Jahrb. f . wiss. 



Bot. 39 : 607-644, 1904. 

 OVERTON, E. Ueber die osmotischen Eigenschaften der Zelle. 



Festschrift Naturf. Gesellsch. Zurich. 1896. 

 PPEFFER, W. Osmotische Untersuchungen. 236 pp., 1877. 

 RUHLAND, W. Beitrage zur Kenntniss der Permeabilitat der 



Plasmahaut. Jahrb. f. wiss. Bot. 46 : 1-54, 1909. 

 VRIES, H. DE. Eine Methode zur Analyse der Turgorkraft. 



Jahrb. f. wiss. Bot. 14 : 427-601, 1884. 

 VAN'T HOFF, J. H. Die Rolle des osmotischen Druckes in der 



Analogie zwischen Losungen und Gasen. Zeitsch. f. phys. 



Chemie. 1 : 481-508, 1887. 

 WACHTER, W. Ueber den Austritt von Zucker aus den Zellen 



der Speichorgane von Allium CepaundBetavulgaris. Jahrb. 



f. wiss. Bot. 41 : 165-220, 1905. 



TEXTS. Barnes, Ganong, Jost, Pfeffer, 



