464 Mr. W. Stiles and Dr. F. Kidd. Position of the 



Meurer's results, however, show no case of the hecaping up of salt inside 

 which takes place with further dilution. This is not surprising, as the 

 concentrations he used all lie between N/IO and N/25, with the exception of 

 one experiment with calcium chloride at N/70 and one with magnesium 

 chloride at N/95. Our own experiments show that with calcium chloride a 

 much greater dilution has to be reached in order to obtain heaping up than is 

 required with potassium or sodium chlorides. 



The absorption ratios observed by Meurer for sodium and potassium 

 chloride are less than those obtained by us, though the time of immersion 

 was twice as long. This quantitative difference may possibly be due iu part 

 to the lower temperature at which Meurer worked (5° C.) as compared with 

 that in our experiments (20° C), but the chief reason is undoubtedly to be 

 found in the thickness of the discs used by him. He worked with slices of 

 tissue 3 mm. thick, while in our experiments the thickness o^he discs was only 

 1 mm. Ruhland (10) has already emphasized the importance of the thickness 

 of the tissue slices used in experimental work dealing with the absorption of 

 salts by tissue from solutions. He compared the absorption by equal weights 

 of 3 mm. and 1 mm. discs of beet in 0-4 per cent, calcium chloride and of carrot 

 in 1 per cent, ammonium nitrate. With neither size of disc did the absorption 

 ratio exceed unity, which agrees with our results for such concentrations, but 

 within the time-limits of his experiments it is seen that the 1-mm. discs 

 absorbed considerably more than the 3-mm. discs. The following Table 

 summarises his results. After allowing for the thickness of the discs in 

 Meurer's experiments, they fall wonderfully into line with our own. 



It is clear that the relation between surface and volume of tissue in 

 experiments dealing with the absorption of salts from solutions needs 

 further examination, but as far as the relation between the absorption ratio 

 and the concentration of the external solution goes, the solution of this 

 question should not essentially modify the results described in the present 

 paper. 



Table XII. — Influence of the Thickness of the Tissue on the Absorption of 

 Salt by Plant Tissue. (Data from Euhland.) 



Carrot seven days in 1 per cent, ammonium nitrate. 



Influence of Thickness of Tissue Slices on Absorption Ratio. 



ThickBess of tissue. 

 3 mm. 

 1 mm. 



Absorption ratio. 

 0-5276 

 0-8342 



