igigl 



MacDOUGAL, RICHARDS, 6- SPOEHR—SUCCULENCE 



409 



In connection with the swelling measurements described later, 

 it became important to ascertain how much acid would leach out 

 during immersion in water. Table II indicates the averages of a 

 considerable number of series. 



It is noticeable that the total amount of acid is somewhat greater 

 than the figures previously given, due very possibly to the forma- 

 tion of acid during immersion in water, which might be caused 



TABLE I 



TABLE II 

 Leaves immersed in w.\ter for 24 hours at i7°c. 



by the exclusion of oxygen. It is also to be observed that the 

 residual acid in the young leaves is closely the same in both the 

 succulent and thin-leaved type. It appears that in the old leaves 

 proportionately less of the acid leaches out and more is retained in 

 the tissues. Other series of experiments were undertaken to 

 determine the rate at which the acid diffuses out, the results of 

 which are given in table III. 



During the first hours of immersion the amount of acid which 

 passes out is small and nearly equal in each case. As prolonged 

 immersion in water kills the leaves, it seems probable that very 

 little acid escapes as long as the cells are alive.^ Table IV indicates 



3 Lauk, E., Die Bedeutung der Elektrolyten fuer Quellungsprocess. Biochem. 

 Zeitsch. 37: 15-58. 1916. 



