I9I9] 



MacDOUGAL, RICHARDS, b- SPOEHRSUCCULENCE 



411 



A set of sections were now prepared, and, after being swelled 

 with reactions parallel to the preceding, were dried, and the expan- 

 sion when immersed was calculated on the original thickness, as 

 follows : 



Determinations were also made of the escape of acid from dried 

 leaves, which, as shown in table VI, is much more rapid than with 

 the living material. It will be seen that the total of the acid 

 extracted from the dried leaves is much less than that obtained from 

 fresh leaves, which, as might be expected, indicates that some of the 



TABLE VI 

 Escape of acid from dried leaves in terms of cc. N/20 koh per gm. fresh 



WEIGHT AT I7°C. 



acid salts are absorbed and held in the irreversible aggregation 

 phenomena connected with the processes of drying. It may be 

 mentioned that two series of both kinds of leaves, which by chance 

 were dried much more slowly than the others, showed a difference in 

 the rate at which they yielded up their acid; in both cases the 

 amount which escaped in 2 hours was much less than in the case 

 of the rapidly dried leaves. 



When trios of leaves of the 2 types were placed under the auxo- 

 graph to determine their unsatisfied hydration capacity, sweUings 

 as follows (table VII) were displayed at 16° C. 



As will be seen by comparisons with data obtained from Castil- 

 leja, the dried mass behaves like the succulent leaves by showing 

 but little expansion after immersion and drying. 



Similar tests were appHed to sections and to dried median 

 slices of an unknown Opuntia which appeared to be less muci- 

 laginous than 0. discata. Dried slices came down to a thickness of 



