RESPIRATION AND OXYGEN. 61 



ox3^gen-contents of 20.8, 8, 6, 4, 2, and per cent, the point at which 

 a decrease of the C0 2 production appeared was different for different 

 plants. On an average, however, a striking reduction of the carbon 

 dioxid produced did not take place between 4 and 2 per cent. At 

 2 per cent, flowers of Anemone japonica, fruits of Prunus domestica, 

 and seedlings of Helianthus, Triticum, and Vicia respired normal 

 amounts of C0 2 , while flowers of Stenactis annua, Cacalia verbasci- 

 folia, fruits of Hippophaea, and seedlings of Brassica napus and 

 Cucurbita melanosperma showed a marked decrease of CO 2 . With a 

 number of fruits the amount of CO 2 was not influenced by the oxy- 

 gen-content, since these produced as much C0 2 in hydrogen as in 

 the air. The respiration quotient was not influenced by a content 

 of 8 per cent and an exposure period of 3 to 24 hours, but at 3 to 

 4 per cent of oxygen the quotient was changed, with a resulting 

 increase of CO 2 . 



Ziegenbein (1893 : 564) found that seedlings of Lupinus exhibit a 

 breaking down of the albumen in the absence of oxygen, as well as 

 in its presence. Diakonow (1894) repeated his earlier experiments 

 upon the dependence of molds upon the presence of oxygen, using 

 Penicillium glaucum, Aspergillus niger, and Mucor stolonifer. With 

 the first two, activity was found to be wholly dependent upon oxygen, 

 the excretion of carbon dioxid ceasing instantly in pure hydrogen. 

 Penicillium, moreover, died quickly in the absence of oxygen, even 

 in solutions containing sugar or glycerin. Mucor, on the contrary, 

 showed no injury when grown in a sugar solution, and continued to 

 produce C0 2 in a stream of pure hydrogen. 



Palladin (1894), in applying Diakonow's discovery to flowering 

 plants, found that, while etiolated leaves of Vicia faba and Lupinus 

 luteus, free from carbohydrates, evolved but small amounts of C0 2 

 and quickly died in the absence of oxygen, those that had absorbed 

 sugar produced carbon dioxid much more rapidly and retained their 

 activity longer. 



Godlewski and Polzeniusz (1897) showed that peas in oxygen-free 

 media were able to use 40 per cent of their original weight in respira- 

 tion. In spite of the accumulation of alcohol in the culture, intra- 

 molecular respiration continued for 6 weeks, the intensity being 

 maintained for 3 weeks at the level of that of normal respiration. 

 They also showed that the seeds retained their power of germination 

 for 2 weeks under anaerobic conditions. 



Buchner (1897 : 117) first showed that yeast contains a ferment, 

 zymase, capable of transforming glucose into alcohol and C0 2 . 

 Devaux (1899) found that the deep-seated tissues of woody stems 

 above a certain diameter are lacking in free oxygen, and hence 

 undergo fermentation with the formation of carbon dioxid and 

 alcohol. This condition exists at ordinary temperatures, but is 

 augmented by raising the temperature. Direct analyses of the gas of 



