Mason — Electrolytes in the Leaf-sap of Syringa vulgaris. 661 



altering the concentration of electrolytes, it is evident that the application of 

 the linear viscosity correction as a means of ascertaining the quantity of 

 electrolytes in the sap is liable to be misleading, and recourse must be bad 

 to ascertaining the loss in conductivity which takes place in some salt after 

 its solution in the sap. 



The Concentration of Electrolytes in the soil solution as a factor in the determina- 

 tion of the variations in electrolyte content of the leaf. 



It is now possible to resume the investigation of the factors responsible 

 for the fluctuations in the amount of electrolytes already encountered in the 

 leaf-saps of Syringa vulgaris. If it be assumed that the electrolytes are 

 mainly inorganic, and have been ultimately drawn from the soil solution, it 

 seemed probable that an examination of the conductivities of the soils from 

 which the material was obtained might prove of value. 



The samples of soil were taken from under the trees at a depth of three 

 inches. After the removal of the stones and coarser particles had been 

 accomplished by passing the soils through a sieve, 250 c.c. of each sample were 

 measured in a graduated cylinder, which was then tapped on the ground till 

 no further shrinkage in volume could be observed. The soils were then 

 transferred to a filter [with filter paper], and 300 c.c. of distilled water 

 gradually added. 



The conductivities of the filtrates are shown under C, in Table IX. The 

 saturated soil, which remained on the filter, was centrifuged after twenty-four 

 hours ; the conductivities of the solutions thus obtained are shown under C 2 . 

 The soils were, as the moisture contents in the table indicate, at the time of 

 sampling very dry ; the drain on the soil-moisture is, of course, very great 

 under a rapidly transpiring tree. 



As it may be doubted whether the above method is capable of furnishing 



