498 Mr. W. Stiles and Dr. F. Kidd. The Comparative 



.as far as the conditions of experiment allow. The most noteworthy fact 

 brought out from this Table is the much smaller total absorption of calcium 



.and magnesium than of potassium and sodium, and the much smaller total 

 absorption of sulphate than of chloride and nitrate. Potassium is always 

 absorbed to a slightly greater extent than sodium, while the indication is that 



^nitrate is absorbed somewhat more than chloride. The results will now be 



•discussed in the following section, where the results of some other workers 

 will be compared with those here recorded. 



■ Table IX. — Ratio of Salt Concentration in Tissue to that in External Solution 

 after Intake of Salt from Solutions in lSr/50 Concentration having a 

 common Kation or Anion. 



Salt, N/50. 



Absorption ratio. 



\ Salt, N/50. 



Absorption ratio. 



Chloride series, 91 hours 



KCl 



NaCI 



LiCl 



CaCl. 



Sulphate series, 64'5 hou 



K2SO4 



Na,SO, 



MgS04 



3-58 

 3 -49 

 1 16 

 1 -09 



rs — 



-51 

 0-46 

 0-097 



Nitrate series, Yl'S hour 



KNO3 



NaNOs 



Ca(N03). 



A1(N03)3 



Potassium series, 42 hou 



KCl 



KoSO, 



KNO3 



3 — 



4-65 

 3-30 

 1-19 



0- 53 



rs — 



1- 99 

 0-55 



2- 20 



Discussion. 



In an earlier paper we have shown that the rate of intake of salts by plant 

 tissue depends on the concentration of the solution from which absorption 

 takes place, and that the equilibrium reached in salt intake depends very 

 greatly on the concentration, a relatively less proportion of the salt being 

 ..absorbed with increasing concentration. In attempting to determine the 

 relative rates of absorption of different salts or ions it is therefore essential 

 .that the salts compared should be presented to the tissue in equivalent 

 xjoncentration. The data recorded in these pages have been obtained with 

 concentrations of N/50. 



It is first necessary to discuss how far the results obtained by the 

 conductivity method justify a comparison of the rates of intake of different 

 salts. 



If the salt is absorbed without exosmosis resulting, and if the two ions of 

 the salt are absorbed in equivalent quantities, the decreases in conductivity 

 will be very close measures of the absorption of the salt. The increase in 

 the degree of dissociation resulting from dilution will be slight, and as all the 

 ..salts compared are absorbed more or less, a slight increase in the degree of 



