Mason — Electrolytes in the Leaf-sap of Syringa vulgaris. 657 



As this matter is more fully dealt with in subsequent experiments, it is 

 possible to proceed now to a consideration of the nature and magnitude of 

 the fluctuations in electrolyte content encountered in the leaf- saps of a 

 number of Syringa vulgaris trees growing in different parts of the County 

 Dublin, and to briefly describe the five localities referred to in Table IV. 



On the Variations in the Concentration of Electrolytes in the Leaves of Syringa 



vulgaris. 



Of these areas, only the grounds and Botanical Gardens of Trinity 

 College are exposed to town conditions ; the latter is not exposed to quite 

 the same amount of smoke as the former, but in both cases there is of course 

 a considerable reduction in the intensity of the light available for carbon 

 assimilation. 



The third area, the Scalp, is situated among the hills about ten miles 

 south of the city ; carbon assimilation may be here possibly somewhat limited 

 by the temperature. 



The Milltown and Island Bridge areas are both a few miles outside 

 Dublin, and neither is exposed to the smoke of the city. 



A survey of the figures recorded in the two conductivity columns [C the 

 observed conductivity, and C v the- conductivity corrected &r -the viscosity] 

 indicates that though the application of the viscosity correction has con- 

 siderably altered the ratios, yet the order of magnitude [in brackets} of the 

 conductivities has been only very slightly changed. It would seem from 

 this that for comparative results, where the fluctuations are marked, the 

 viscosity correction may be dispensed with. 



It should be pointed out, however, that the corrected conductivities [C*] 

 are somewhat too high ; this is especially so in the Island Bridge samples. 

 The magnitude of the over-correction will be subsequently indicated. 



If the results recorded for the five areas be compared, it will be seen that 

 those areas where a high non-electrolyte content prevails in the leaf-sap 

 usually show a relatively low concentration of electrolytes. It may be also 

 noticed that a similar tendency is encountered among the saps of individual 

 areas. The Island Bridge results are, however, in this respect exceptional. 



The part played by the Colloids of the Sap in Retarding the Mobility of the Ions. 



The tendency to over-correction, to which the application of the linear 

 viscosity-conductivity correction leads, is a subject which must now be 

 referred to. 



As a precipitate of gums was thrown down, on adding basic lead acetate 

 or alcohol to the filtered sap, it seemed probable that the overcorrection might 



