Mason — Inhibition of Invertase in the Sap of Galanthiis nivalis. 87 



containing test-tubes in boiling water, the variation in the amount of protein 

 precipitated was very marked. The amount in the sap pressed from the 

 untreated leaves was almost double that of the frozen, while that from the 

 toluene material was very slight. On storage at room-temperature differences 

 in the amount of precipitated colloids of the same order were observed in the 

 untreated and frozen samples, though none could be detected in that pressed 

 from the toluened leaves. 



With ferric chloride a dark green colouration was produced in all samples, 

 but, as gelatine was not precipitated, it is improbable that a true tannin was 

 present. 



The changes in the depression of the freezing-point during a storage of 

 seventy-two hours at 29° are shown in Table V. 



The term " sap + sucrose" in the table refers to samples in which 25 c.c. 

 of each sap were added to two grams of sucrose. 



Both the saps and the sap -i- sucrose solutions were stored in small flasks, 

 previously sterilized, and fitted with rubber corks. A little toluene was 

 added before each observation in order to ensure that the samples were 

 completely saturated. 



To make an observation 5 c.c. were withdrawn from each flask, and stored 

 at 0° till all the observations were complete. The samples used for the 

 determinations of the freezing-points were then returned to their respective 

 flasks. 



Table V. 



