88 



Scientific Proceedings, Royal Dublin Society. 



Figures 1, 2, and 3 show these changes in the depression of the freezing- 

 point graphically represented. The depressions on the left and right of the 

 figs are those of the sap + sucrose solutions and saps respectively. 



1-318 



20 



30 40 50 



TIME IN HOURS. 



Fig. 1. 



60 70 



0-838 



SO 



The increase in the depression of the freezing-point of both frozen and 

 untreated samples is, doubtless, due to the inversion of sucrose; the 

 interpretation of the subsequent changes in the depression is not clear. The 

 presence of factors inhibiting the hydrolysis of sucrose is, however, indicated. 

 In the toluened samples this is very marked, but, as there is very little 

 indication of any hydrolysis, it may be that exposure to toluene vapour has 



A 

 1-287 



1-267 



1-24-7 



1-227 



1-207 



SAP 



FROM 



TOLUE 

 VES 



NED 



A 



p-810 



0-790 



0770 



O 



10 



20 



30 40 50 60 70 

 TIME IN HOURS 



Fig. 2. 



destroyed the enzyme. That this is unlikely is indicated by the fact that 

 toluene has no toxic effect on the invertase of yeast. It may not be without 

 significance that the amount of sucrose inverted in the three samples is 

 roughly proportional to the colloids precipitated on storage. The clumping 

 of the colloids of the sap after its extraction from the leaf is very striking, and 

 has been observed in the extracted sap of a number of plants. 



It was considered possible that the addition of a little saponin to the 



