Mason — Inhibition of Invertase in the Sap of Galanthus nivalis. 95 



indicated ; in the sucrose sample hydrolysis of sucrose is possibly masked by 

 this condensatiDn. 



In the next experiment sap was pressed from leaves gathered at 9.30 a.m., 

 March 25th. Saps pressed from both frozen and untreated leaves were 

 used ; 1 c.c. and 0'5 c.c. respectively of each sample were added to 5 c.c. of 

 a 6 per cent, sucrose solution. Toluene was not used. 



Table XI. 



The changes in depression of the sucrose sap solutions of the untreated 

 leaves are somewhat similar to those of the night sucrose samples of fig. 4. In 

 the frozen samples, however, the initial steep rise in depression is absent. 



Discussion. 



The results obtained, though difficult to interpret, indicate that factors 

 inhibiting the activity of the enzyme responsible for the hydrolysis of sucrose 

 may be present in the sap. It has been pointed out that changes of a nature 

 not yet understood (possibly, as Dr. Atkins has suggested to the writer, in 

 the concentration of hydrogen ions) occur in the sap after its extraction from 

 the leaf, which lead to a clumping of the colloids. It is suggested that the 

 enzyme may be inactivated by adsorption on the coagulated colloids. 



Thus the inactivity shown by the toluened sap would be due to the removal 

 of the invertase by the precipitation of the colloids before the extraction of 

 the sap from the leaf ; the absence of a colloid coagulum on storage supports 

 this view. It is unnecessary to consider the factors which might lead to this 



