EXPERIMENTAL DATA OF DETERMINATIONS. 



59 



TABLE 35. Evolution of CQi in sunlight and in diffuse light, compared with that in darkness. 



The experiment was made with Opuntia versicolor, at Tucson, July 23, 29, 30, 31, and 

 August 2 and 3, 1912. The joints exposed to sunlight were in a glass receiver immersed in 

 water cooled with ice; those in diffuse light were in the same receiver and were placed out 

 of doors in the shade. The apparatus was very carefully tested after the determinations, 

 to make sure that there could be no vitiation of the result from leakage. After running 

 blank for 3 hours without any plants in the receiver no trace of CO 2 was found. 



TABLE 36. Wound respiration. 



Series I consisted of 8 mature joints of Opuntia versicolor, with a fresh weight of 120 

 grams, and was begun April 10 at 8 a. m., and wounded at lO^O" 1 a. m. Series II consisted 

 of 7 joints of the same plant, with a fresh weight of 132 grams, and was begun at 2 p. m. 

 April 10 and wounded at 7 h 30" p. m. The temperature throughout was 25 C. After 

 determination of normal respiration, wounding was effected by slicing the joints into sec- 

 tions 10 to 15 mm. thick. The experiments were made at New York, April 10 to 12, 1912. 



