Senile Changes in Leaves of Ceetain Plants 



339 



greater power of imbibition in the cellulose and protoplasm of the young 

 tissues, or, as Fischer (1910) has shown, to a greater degree of acidity in 

 the younger cells. That Fischer's results for animal colloids hold, to some 

 degree at least, for plant colloids, is indicated by the following test: In 

 the bottom of each of six graduated glass tubes was placed 0.2 cubic cen- 

 timeter of leaf powder from the old leaves, and into each tube was poured 

 2 cubic centimeters of distiJed water or of the concentrations of oxalic 

 acid indicated below. The concentration of oxalic acid is expressed in 

 terms of gram-molecular solution. The results are shown in table 53: 



TABLE 53. 



Effect of Different Concentrations of Oxalic Acid on Absorption 

 OF Water by Powdered Leaves 



Test tube 



Added 2 cubic centimeters of 



Time 

 (hours) 



Height 



of colunm 



of swollen 



powder 



(centimeters) 



A 



Distilled water 



24 

 ?4 

 24 

 24 

 24 

 24 



2 8 



B . . 



. 005 oxalic acid 



3 8 



C 



. 02 oxalic acid 



4 5 



D 



. 1 oxalic acid 



3 8 



E 



. 5 oxalic acid 



3 3 



F 



Distilled water 



2 7 









The swelling was greater in the weak acids than with distilled water, 

 and reached a maximum at 0.02 molecular solution of oxalic acid. 



The fact that the powder from the young leaves swells more than 

 that from the old leaves may therefore be due to the fact that the leaves 

 of the young vines are richer in some organic acid than are those of the 

 old vines. 



RELATIVE ACIDITY OF THE YOUNG AND THE OLD POWDERED LEAVES 



In each test tube 0.2 gram of powder was placed, 2 cubic centimeters 

 of distilled water was added, and the test tube was shaken. The acidity 

 of the water was then neutrahzed by titrating with 0.1 normal KOH, 



