546 



The Influence of Temperature on the Absorption of Water by 

 Seeds of Hordeum vulgare in Relation to the Temperature 

 Coefficient of Chemical Change. 

 By Adman J. Brown, F.K.S., and F. P. Worley, M.A., M.Sc, New Zealand. 



(Received August 9, 1912.) 



Attention has previously been directed by one of us to the existence of a 

 differential septum enclosing the seeds of Hordeum (barley).* When the 

 seeds are immersed in aqueous solutions of most electrolytes, and of many 

 non-electrolytes, this covering behaves as a very efficient differential septum, 

 water alone entering the seeds under the attractive influence of the finely 

 granulated contents. 



The rate at which the water enters is considerably affected if substances 

 are dissolved in it, being increased by some and diminished by others ; it is 

 .also markedly dependent on the temperature of the water or solution in 

 which the seeds are immersed. Variations of the rate at which water enters 

 with alterations of the experimental conditions are presumably due mainly 

 ,to changes in the water, and the seeds of Hordeum would thus appear to be 

 a very suitable medium for the investigation of the nature of the changes 

 produced in water by the presence of dissolved substances or by alterations 

 of temperature. 



In this communication, attention will be confined to the influence 'of 

 temperature on the rate at which water is absorbed by the seeds of 

 Hordeum vulgare. 



Known weights of the seeds were immersed in water at definite 

 temperatures constant to within 07° throughout the experiments. The mean 

 temperatures at which observations were made are 3"8°, 21-1°, and 34-6°. 

 After different intervals of time, the weight of the water absorbed by the 

 -seeds was ascertained by removing the seeds from the water, rapidly drying 

 the surfaces, and then weighing. After weighing, the seeds were immediately 

 returned to the water, and soaked during a further period. 



The results of one series of observations are recorded in the following 

 table, and shown graphically in the accompanying diagram (I). 



It will be noticed that, during the earlier stages of the experiment, the 

 rate at which the entry of water takes place increases very rapidly as the 

 temperature rises ; subsequently, when the saturation point is approached, 



* 'Boy. Soc. Proc.,' 1909, B, vol. 81, p. 82. 



