74 



ACIDITY AND GAS INTERCHANGE IN CACTI. 



of illumination, prolonged darkness, or rise of temperature, and there may be 

 others concerning which we have no data. The splitting of the acid demands 

 a greater absorption of oxygen and results in still greater formation of carbon 

 dioxide, so that the ratio must also rise until it approaches unity or even, in 

 some cases, exceeds it. Where the ratio is increasing it must mean that some 

 carbon dioxide is being formed without the intervention of atmospheric 



TABLE 49. General averages of 102 gas-interchange determinations made during the summers 

 of 1912 and 1913, arranged according to ratios and grouped according to temperatures. 



'These four results not included in average. 



