378 



Prof. A. J. Brown and Mr. F. Tinker. 



Conversely, the position of the equilibrium point gives an indication of the 

 extent to which the solute enters the seeds. Table V shows a series of 

 organic solutes arranged approximately in the order of the equilibrium points 

 they give,* and therefore in the order of the extent to which the solute enters. 

 The surface tensions of the solutions are given in certain cases also.f 



Table V. — Showing Order of Extent to which Various Organic Solutes Enter 



the Barley Seeds. 



Solute (molar). 



irercentage increase in weignfc 

 when seeds are immersed 

 in molar solution. 



Surface tension of molar 

 solution (Traube). 







dynes/cm. 





39 -3 



76 5 





40 -8 



75 -7 





41 -5 



74 -1 





41 -8 



75 -3 





42 -2 







45 -2 



74 -8 





52 -7 



71 -8 





61 -4 







63 -4 







66 -6 







68 -7 



56 -2 





68 



61 -5 





69 -6 



57 -9 





71 -8 



43 '2 



N/2 phenol 



85 -0 



43 -3 



The explanation of this relation between the relative concentrations of the 

 inside and outside solutions is quite simple. When there is a difference 

 between the two concentrations in question, an extra osmotic force is- 

 introduced into the system beyond the forces which are present when there 

 is no concentration difference. If the seeds are immersed in pure water, for 

 instance, diffusion merely takes place until the surfaces of the colloidal 

 contents are saturated with moisture. But, if the seeds are immersed in a 

 solution, and the membrane acts selectively towards the latter, there is an 

 outward or inward osmotic force according as the solution inside is weaker 

 or stronger than that outside. In the former case the colloidal contents of 

 the seeds will be prevented from taking up as much liquid on to their 

 surfaces as they would otherwise do, so that the equilibrium point will be 

 lowered. In the latter case still more solution will be driven into the seeds^ 

 and the equilibrium point raised. 



* This Table is compiled from a previous paper, 'Roy. Soc. Proc.,' B, vol. 81, p. 82 

 (1909). The order is only approximate. 



t The surface tensions are taken from J. Traube's paper, ' Journ. Phys. Chem.,' vol. 14, 

 p. 460 (1910), and other papers. 



