86 



Scientific Proceedings^ Royal Dublin Society. 



unconnected with the presence of micro-organisms on the surface of the 

 material, some leaves were immersed for six days in a little freshly boiled 

 water. The water was then decanted off, and to 220 c.c. were added 7'7gms. 

 of sucrose. The solution was divided into two parts, one of which was boiled. 

 Both were saturated with toluene. After nine days' incubation at 29° C, 

 there was no evidence of inversion in either sample ; thus the enzymes set free 

 from micro-organisms do not appear to have been responsible for any of the 

 rise in depression recorded in Tables I and II. 



In the next experiment the leaves of a clump growing in the open were 

 divided into three parts. The leaves were gathered at 10 a.m. on April 30th. 

 The first sample was pressed immediately without any treatment, the second 

 was exposed to toluene vapour for five hours in a sealed chamber, while the 

 third, enclosed in a test tube, was immersed in a salt-ice freezing mixture 

 (-16°) for two hours. About 60 c.c. of sap were collected from each sample, 

 and filtered and stored overnight at 0°. 



The depressions of freezing-point and the electrical conductivities are 

 shown in Table IV. The conductivity observations were made at 0°, and are 

 liable to a correction allowing for the viscosity of the saps. As the saps 

 were saturated with toluene, 0-02° (the depression of the freezing-point of 

 water saturated with toluene) has been subtracted from the observed 

 depressions. Toluene was not added to the saps on which the conductivity 

 measurements were made. 



Table IV. 



That exposure to toluene vapour has not rendered the protoplasm 

 completely permeable is indicated by the greater depression of the sap 

 pressed from the frozen leaves ; the difference, however, may be due to a 

 partial destructon of sugar owing to the stimulation of respiration by the 

 antesthetic. 



On immersing the three samples of sap for one minute with their 



