Rate of Absorption of Various Salts by Plant Tissue. 503 



absorbed to a much less extent than potassium, sodium, chloride, and 

 nitrate. 



Summary. 



1. The rate of absorption of various chlorides, sulphates, nitrates, and 

 potassium salts from solutions of 0'02 N concentration was measured by the 

 electrical conductivity method previously described. 



2. After a brief initial period, lasting only a few hours, of rapid withdrawal 

 of salt from solution, there follows a long period, lasting several days, during 

 which absorption proceeds to an equilibrium. Over this period the curve 

 follows an approximately logarithmic course. 



3. Rations appear to be absorbed initially in the following order : 

 K, [Ca, Na], Li, [Mg, Zn], Al. The position of ions enclosed within brackets 

 may have to be reversed. This initial order of the rate of absorption does 

 not indicate, however, the extent to which the ions are absorbed when 

 equilibrium is approached ; the order of absorption is then K, Na, Li, [Ca, Mg], 

 the chief difference between this order and the initial order being in the 

 position of Ca, which is absorbed to only a slight extent compared with 

 K and Na. 



4. Anions appear to be absorbed initially in the order SO4, NO3, CI, which 

 gives place later to the order NOs, CI, SO4 on account of the comparatively 

 slight extent to which the sulphate ion is absorbed. The difference between 

 nitrate and chloride is slight, and stress should not be laid on it. 



0. These results agree in general with those of Kuhland, Fitting, Pantanelli, 

 and Troendle, using different methods and different experimental material. 

 These workers, however, did not distinguish between differences in the initial 

 rates of absorption and differences in the position of equilibrium. 



6. It seems clear that the rate and extent of intake of one ion of a salt 

 may be influenced by the nature of the other ion. 



7. The results obtained in regard to aluminium support the observations of 

 Eothert and Meurer that this ion is rapidly absorbed from aluminium 

 sulphate. This proceeds much more rapidly than the absorption of the 

 anion. 



8. Although Troendle's view that in any group of the periodic classifica- 

 tion the metallic ions are absorbed more rapidly the higher the atomic weight, 

 is not contradicted, yet the view that the initial rate of absorption is largely 

 dependent upon the mobility of the ions or diffusibility of the salt is equally 

 well supported, and can be put forward provisionally as a more reasonable 

 hypothesis. 



The position of equilibrium appears, however, to be governed by some 

 quite different property, as to the nature of which it would be premature at 



2 E 2 



