119 



Hie Rate of Absorption of Various Phenolic Solutions by Seeds 

 0/ Hordeum vulgare, and the Factors Governing the Rate of 

 Diffusion of Aqueous Solutions across Semipermeable 

 Membranes. 



By Adrian J. Browx, F.B.S., and Erase: Tinker, XL Sc. 

 (Received August 27. 1915.) 



It has been pointed out previously* that the seeds of Hordeuni (barley) 

 are enclosed by a membrane which exhibits the exceptional property of 

 differential permeability, and that use may be made of this property of the 

 seeds for the purpose of investigating some of the obscure phenomena 

 associated with osmosis.f 



"When the dry seeds are immersed in aqueous solutions of most inorganic 

 acids and salts, sugars, etc., water only passes through the containing 

 membrane and moistens their starchy contents ; with other classes of 

 solutes, however, such as the phenols, fatty acids, and monohydric alcohols, 

 the solute enters the seeds together with water. A dry seed of Hordeum 

 may be regarded, therefore, as a diffusion system consisting of a mass of 

 solid material capable of absorbing moisture, enclosed within a differentially 

 permeable membrane. In the presence of those solutes which do not enter 

 the seed-diffusion-system along with the solvent the action of its membrane 

 is comparable to that of a copper-ferrocyanide membrane in contact with 

 sugar solution. On the other hand, in the presence of those solutes which 

 do enter the seed-diffusion-system together with the water, its membrane 

 evidences a property of selective permeability only recognised to any extent 

 with living protoplasm, and with the coverings of certain seeds. 



Previous investigations carried out by methods of experiment already 

 described have demonstrated that when seeds of Hordeum are immersed in 

 solutions of solutes to which the seeds are impermeable, less water enters 

 the seeds than from pure water, and that the actual amount entering is 



* A.. J. Brown, " On the Existence of a Semipermeable Membrane enclosing the 

 Seeds of some of the Graminese,." ' Annals of Botany,' vol. 21, p. 79 (1907) ; " The 

 Selective Permeability of the Coverings of the Seeds of Hordeum. vulgare" ' Roy. Soc. 

 Proc.,' B, vol. 81, p. 82 (1909) ; A. J. Brown and F. P. Worley, " The Influence of 

 Temperature on the Absorption of Water by Seeds of Hordeum vulgare,' 'Roy. Soc. 

 Proc.,' B, vol. 85, p. 546 (1912). 



t The seed of the sub-species of Hordeum (barley) known as Hordeum vulgare has been 

 found especially suitable for experimental purposes, and has been employed in the 

 following investigation. 



