62 



ACIDITY AND GAS INTERCHANGE IN CACTI. 



TABLE 40. Respiration with continuously changing temperature. 



The temperature variation is about that of an April day in Tucson. Determinations made 

 in New York, March 22 and 23, 1912, the material being 15 mature joints of Opuntia versi- 

 color of the previous season's growth, with a fresh weight of 180 grams, sent from Tucson . 



TABLE 41. Respiration with continuously changing temperature. 



Made at New York, May 8 and 9, 1912, with material sent from Tucson. This material 

 consisted of 18 mature joints of Opuntia versicolor of the previous season's growth, with a 

 fresh weight of 354 grams. Previous to determination the plant was subjected to a tem- 

 perature of 30 for several hours. 



