92 Prof. A. J. Brown. Selective Permeability of the [Jan. 23, 



Table IX. 



Solute. 



Percentage of water absorbed during— 



2 days. 



4 days. 



7 days. 



9 days. 



11 days. 



Ethyl alcohol 



43 -4 



54 -9 



66 -9 



68 -7 



69 -6 



Ethylic acetate 



63 -9 



70 -7 



72 -8 



72 -1 



71 -8 



Acetic acid 



53 -3 



67 -6 



68 -3 



68 -5 



68-0 



Water (control) 



45 -0 



55 -6 



65 -5 



68 -9 



70-5 



NaCl (control) 



30 -9 



34 -4 



35 -8 



36 -8 



36 -5 



substances do not diffuse through the seed-coverings in the absence of water, 

 although they all diffuse readily into the interior of the grain from their 

 aqueous solutions. 



It is also interesting to note the manner in which the velocity with which 

 the different solutions are absorbed varies. The solution of ethyl alcohol 

 enters comparatively slowly, at about the same rate as pure water ; that of 

 acetic acid enters more rapidly ; whilst the rate of entry of the solution of 

 ethylic acetate is markedly the most rapid of the three. Nevertheless, 

 despite the differences of velocity, equilibrium is established between the 

 seeds and the three solutions at approximately the same point. 



A further series of observations with solutions of non-electrolytes are 

 recorded in the following table : — 



Table X. 



Solute. 



Percentage of water 

 absorbed. 





41 -5 





41 -8 





45 -5 



Ethylene glycol 



52 -7 





36 -5 





20-5 



The results obtained with glycerol and glycine resemble those afforded 

 by cane-sugar and dextrose (see Table III), but differ very markedly from 

 those obtained with such compounds as alcohol and acetic acid. The 

 behaviour of glycine or amino-acetic acid is particularly interesting, as this 

 compound differs to so slight an extent in constitution from acetic acid. 

 Urea and ethylene glycol have less influence than either glycerol or glycine ; 

 glycol, however, although it differs to so slight an extent from alcohol in 

 constitution, is far more effective in preventing the entry of water. 



