AEROBIC AND ANAEROBIC RESPIRATION. 



65 



hydrogen therein. The hydrogen was prepared from c. p. zinc and sul- 

 phuric acid and was washed through a solution of 10 per cent lead nitrate 

 and one of 10 per cent silver nitrate. The oxygen in the bell- jar was con- 

 sumed slowly, and when the flame went out the hydrogen was immediately 

 turned off. By means of a bent glass tube and a burette, oxygen-free water 

 was added then to the dish containing pyrogallol and KOH. Thus the last 

 traces of oxygen were removed from the atmosphere in the bell-jar. In all 

 probability the cactus joints contained some oxygen, but from all indica- 

 tions this was soon used up. 



The plants were allowed to remain thus for 7 days, when they were 

 analyzed in the usual manner. The results are given in table 30. 



TABLE 30. Carbohydrate-content of Opuntia phceacantha in original condition and 

 after having been kept in air and in an atmosphere free of oxygen for 7 days. 

 Values in percentages of the dry material. 



It is evident that under anaerobic as well as aerobic conditions, consider- 

 able amounts of carbohydrates are consumed. This fact was established 

 long ago by Lechartier and Bellamy 1 for fruits. It is, however, noteworthy 

 that the plants under anaerobic conditions consumed as much or even 

 slightly more carbohydrate material than those kept in air. The conclusion, 

 therefore, seems justified that the CO 2 emission, under anaerobic conditions, 

 previously referred to, was the result of carbohydrate respiration. 



A similar experiment was carried out, using Opuntia versicolor. The 

 same method and procedure were followed as in the preceding experiment 

 The plants remained under the experimental conditions for five days. The 

 results are given in table 31. 



TABLE 31. Carbohydrate-content of Opuntia versicolor in original conditions and 

 after having been kept in air and in an atmosphere free of oxygen for 5 days. 

 Values in percentages of the dry material. 



1 LECHABTIEB, G., and F. BELLAMY. 

 466, 1809. 



De la fermentation des fruits. Compt. rend., 69, 



