76 



ACIDITY AND GAS INTERCHANGE IN CACTI. 



acidity group of some experiments with material of very high acidity, so that 

 the rate is higher than it should be. It is, of course, realized that in assembling 

 the averages of these experiments, which are necessarily diverse because of 

 the number of variables, there must be considerable irregularity in the results. 

 It must be remembered that data from material in all conditions are included, 

 both turgid and flaccid, mature joints and young ones. Notwithstanding 

 this, the general tendencies stand out pretty clearly to support the conclusions 

 already drawn regarding the association of high values in acidity, rate of gas 

 interchange, and ratios of carbon dioxide evolved with oxygen absorbed. But 

 this question has been discussed and requires no further treatment. 



It is noticeable in table 50 that in the two lowest groups, which include 

 material with dry-weight acidity up to 3.00 per gram, the upper limit of acidity 



TABLE 50. Averages of 99 gas-interchange experiments made during the summers of 1912 

 and 1913, arranged according to acidity per gram dry weight. 



Averages of 99 gas-interchange experiments made during the summers of 1912 and 

 1913 are given in table 50, arranged according to acidity per gram dry weight expressed in 

 terms of cubic centimeters of N /10 KOH. The temperature groups correspond to the mean 

 temperatures at which the majority of the experiments were conducted. In every case the 

 acidities are expressed in terms of cubic centimeters of N /10 KOH per gram dry weight, 

 and the amounts of COz evolved and Oj absorbed in cubic centimeters of gas per gram 

 per hour. 



