IX 



METHODS OF EXTRACTING SAP 



177 



chloroformed leaves is evidently much greater than can 

 be assigned to the action of the chloroform on the sap, or 

 to the spontaneous changes in the cells of the leaves, 

 which appear in Experiments 229 and 232 respectively. 



Another result which could be interpreted in the same 

 sense was furnished by two experiments on the sap of 

 leaves of Ilex aqui folium. In these it was found that, if 

 the leaves were killed by heat in a saturated atmosphere, 

 they yielded a sap having a much greater depression of 

 freezing-point than that pressed from similar leaves which 

 had not been heated. 



Table 21. 

 Sap from Fresh and Heated Leaves of Ilex aquifolium. 



No. of 

 Expt, 



430 

 431 



Description of Sap. 



Sap pressed from fresh leaves 



Sap from leaves heated to 97 C. for 30 minutes 



Again, it was found that, if a weighed quantity of leaves 

 be desiccated, reduced to powder, and again made up to 

 the original weight with water, the sap pressed from the 

 mass will have a much greater depression than that pressed 

 from the fresh leaves without passing thiough this treat- 

 ment. This point is borne out by the following experi- 

 ments : 



Table 22. 

 Sap from Fresh and Desiccated Leaves of Hedera helix. 



N 



