Physiologie. 313 



Brown, A. J. and F. Tinker. The rate of absorption of 

 various phenolic Solutions by seeds of Hordeum vulgare 

 and the factors governing the rate of diffusion of 

 aqueous Solutions across semipermeable membranes. 

 (Proc. Roy. Soc. LXXXIX. B. 611. p. 119—135. 1915.) 



The seeds of Hordeutn vulgare are enclosed by a membrane 

 possessing differential permeability. In aqueous Solution of most 

 salts, acids etc., water only is absorbed by the seeds, but in 

 Solutions of phenols, fatty acids or monohydric alcohols, both 

 solute and solvent enter the seed. 



In Solutions of the latter class, the rate of entry of water is 

 partly dependent on the nature of the solute and the concentration 

 of the Solution. Detailed experiments were made using the phenols, 

 phenol, catechol, resorcinol, quinol and pyrogallol, as a series of 

 solutes all of which are able to penetrate the barley membrane. 

 An examination ot the results shewed that the rate at which the 

 seeds absorb any Solution is dependent on the amount of Solution 

 which has already been taken up („degree of fulness") as well as 

 on the nature of the Solution. The relation between the absorption 

 rate and the degree of fulness at any temperalure is a linear 

 one. Absorption constants were calculated, giving a measure of 

 the relative rates at which a particular Solution will enter the seed 

 at all degrees of fulness. The absorption constants of all the 

 phenolic Solutions are greater than that of water, except in the 

 case of pyrogallol. The constants increase greatly in value with 

 slight rise in temperature. The variations in rate of diffusion of 

 the phenolic Solutions appear to be associated primarily with diffe- 

 rences in their surface tensions. E. M. Delf. 



Dixon, H, H. and W. R. G. Atkins. Osmotic Pressure in 

 Plant s. VI. On the composition of the sap in the con- 

 ducting tracts oftrees at different levels and at dif- 

 ferend seasons of the year. (Sei. Proc. Roy. Dublin Soc. 

 XV. NO 6. p. 51—62. 1916.) 



Large amounts of sap may be centrifuged from the conducting 

 wood of trees. This contains both electrolyies and non-electrolytes 

 (sugars) in Solution. 



In late autumn and winter, the osmotic pressure of the wood 

 of deciduous trees is low and is nearly constant in all parts of 

 the plant. In early spring the sap receives large quantities of 

 sugars from storage cells of the wood parenchyma and from the 

 medullary rays.; hence its osmotic pressure rises especially in 

 the Upper regions. In late spring the sugar concentration is less 

 but the electrolytes in the sap increase in amount. In evergreens, 

 the seasonal changes are less striking, but in most trees examined 

 both reducing sugars and hexoses are present. E. M. Delf. 



Ewart, A. J„ On the Function of Chlorophyll. (Proc. Roy. 

 Soc. LXXXIX Ser. B. 309. p. 1-17. 1915.) 



The author concludes that experimental evidence is against the 

 view of Wager that peroxides, — whether organic or inorganic, — 

 are among the products of decomposition of Chlorophyll, xantho- 

 phyll, or Carotin in the presence of oxygen and sunlight. These 



