EXPERIMENTAL DATA OF GAS-INTERCHANGE DETERMINATIONS. 99 



TABLE 65. Intramolecular respiration. 



Opuntia versicolor. Young and mature-turgid material, in atmosphere of hydrogen, 99.5 per cent. 

 Only initial acidity given, in terms of c.c. N/10 KOH. For comparison with acidity determinations. 

 Experiments made at Tucson, Arizona, in July 1912. 



TABLE 66. Gas interchange and acidity with increased oxygen supply. 



Opuntia versicolor. Similar to other experiments except that a great excess of oxygen was supplied. For 

 comparison with acidity determinations in similar atmospheres. Acidity in terms of c.c. N /10 KOH. Experi- 

 ment A and A 1 were made in New York, the others in Tucson in 1912. 



TABLE 67. Gas interchange and acidity, over long periods. 



Opuntia versicolor, young and mature-turgid joints. These experiments were run for a long period 18 

 hours. The CO 2 collected in large quantities in the receiver and in all cases was found on analyses of the gas 

 samples to be over 10 per cent and often as high as 20 per cent. In effect the plants were in an atmo- 

 sphere of increased CO 2 content. In other respects these experiments are similar to those given in tables 54 

 and 55, for which reference may be made for further details. Experiments made at Tucson in June and 

 Julv 1912. 



