Mason — Electrolytes in the Leaf-sap of Syringa vulgaris. 653 



The value of the viscosity correction may be seen from an inspection of 

 the conductivities recorded under C Kcl ; the mean of this column is 0-00695, 

 and the maximum deviation + 0-00044. 



Table I. 

 Aucuba japonica, July, 1919. 



A tendency for the electrolyte content of the sap (A«) to diminish as the 

 concentration of non-electrolytes (A - A„) increases may be also noticed. 



The Mature of the Non-Electrolytic Solutes of the Sap. 



In order to ascertain the part played by electrolytes and non-electrolytes 

 in the production of osmotic pressure, Dixon and Atkins (4) determined both 

 the freezing-points and conductivities of the sap. They were thus enabled, 

 by assigning a depression of the freezing-point which a potassium-chloride 

 solution having a conductivity equal to that shown by the sap would pro- 

 duce, to determine approximately the contribution of the electrolytes and 

 non-electrolytes to the total depression. 



Chandler (3) adopted a similar method in order to discriminate between 

 the electrolytes and non-electrolytes of the cell, but also endeavoured to 

 ascertain the nature of the contribution of the sugars to the total depression 

 of the sap. He found that generally more than half the depression of the 

 sap was due to neither electrolytes nor sugars. Unfortunately he omitted in 

 estimating the electrolytes to make any allowance for the viscosity of the 

 sap ; had this been done, there can be little doubt that his estimate of the 

 part played by the electrolytes would have been considerably augmented. 



In Table I a more accurate estimate of the contribution of the electro- 

 lytes (A„) to the total depression of the sap has been determined, so that it 



5k2 



