340 Hareis M. Benedict 



phenolphthalein being used as an indicator. The powder does not in 

 any way interfere vnth the use of this indicator. 



TABLE 54. Relati-ve Acidity of Leaf Powder from Young and from Old Vines 



Amount (in cubic 



centimeters) of 0.1 normal KOH 



solution 



required to neutralize 0.2 



gram of 









Powder of j^oung leaves 





Powder of old leaves 





2.8 







1.4 





2.8 







1.6 





2.5 







1.6 





2.0 







1.6 





2.0 







1.6 





2.0 







1.6 





2.0 







1.3 





1.9 



Average 



1.3 



Average 



2 2 



1.5 



The powder from the leaves of the young vines, therefore, has a greater 

 degree of acidity than that from the leaves of the old plants. This is a 

 distinct difference between the leaves of plants of different ages. The 

 significance of this difference as regards physiological acti\dty cannot be 

 certainly indicated. It may affect the degree of turgidity and the permea- 

 biUty of the cells of the leaves. 



IMBIBITION AFTER NEUTRALIZATION 



In order to see whether the greater acidity was the sole cause of the 

 greater swelling, experiments were made in first neutralizing the solution, 

 then washing it, and then adding 0.02 molecular solution of oxalic acid 

 and noting whether differences in swelling still appeared. In these experi- 

 ments 0.2 gram of leaf powder was placed in each test tube and 2 cubic 

 centimeters of distilled water was added. Each solution was then neutral- 

 ized with 0.1 normal KOH and washed. Two cubic centimeters of 0.02 

 molecular solution of oxahc acid was then added, with a trace of thjonol, 

 and the tubes were left for twenty-four hours. The wet powder, after 

 being gra\dty-drained for five minutes in the inverted test tube, was 

 weighed and the percentage of imbibed water was calculated as a per- 

 centage of the weight of the dry powder. The results are shown in 

 table 55: 



