ANAEROBIC RESPIRATION 59 



Not all plants change from normal to anaerobic respiration 

 with the same facility. Observations on fungi are especially 

 instructive in this respect. Very active yeasts and Mucora- 

 ceae develop a normal alcoholic fermentation even if the aera- 

 tion is appreciably checked (immersion in a thin film of nutrient 

 solution) and the oxidation processes in their cells are thereby 

 depressed.^ Such a small inducement thus suffices to replace 

 normal respiration by anaerobic cleavage processes in these 

 organisms. The so-called strongly aerobic molds behave quite 

 differently. On the basis of the writer's experience,^ Asper- 

 gillus niger does not produce a trace of alcohol even if the 

 fungus mat is entirely submerged in nutrient solution con- 

 taining sugar, but if the atmosphere above the solution is left 

 with its oxygen. The quantity of oxygen dissolved in the water 

 alone suffices to exclude completely the anaerobic processes. 

 Only with the exclusion of oxygen (not with a deficiency of 

 oxygen) is alcoholic fermentation set going by strongly aerobic 

 molds. The investigations of Wilson,^ Stich,'* and Johannsen^ 

 show that seed-plants are sensitive to a checking of aeration 

 but not to an equal degree. According to Stich, a considerable 

 increase in the value of the respiratory quotient generally 

 results with an oxygen content of 1-4%. This excess produc- 

 tion of COo is to be traced to the participation of anaerobic 

 processes in the metabolism. 



2. THE PRODUCTS OF ANAEROBIC RESPIRATION 



Pasteur's first studies of the anaerobic respiration of plants 

 suggest that CO2 and alcohol are formed in this process just as 

 in fermentation by yeast. However, the question of an iden- 

 tity of anaerobic respiration with alcoholic fermentation could 

 not be raised before the ratio CO2 : alcohol was obtained through 

 quantitative measurements with various plants. In alcoholic 

 fermentation, equi-molecular amounts of CO2 and alcohol 



■ Kostytschew, S. Zentralbl. f. Bakt.. Parasitenk. u. Infektions-krankh. (II) 13 : 490. 

 1904; Kostytschew, S. unci P. Eliasberg. Z. f. physiol. Chem. iii : 141. 1920. (C/. also 

 Meyerhof citation in note 2, page 9-1 



2 Kostytschew, S. und M. Afanassjewa. Jahrb. f. wiss. Bot. 60: 628. 1921. 



' Wilson. Untersuch. aus d. bot. Inst. Tubingen, i : 685. 1881-1885. 



» Stich, C. Flora. 74: i. 1891. 



^ Johannsen, W. Untersuch. aus d. bot. Inst. Tubingen, i: 716. 1881-1885. 



