THE CHEMICAL PROCESSES IN PLANT RESPIRATION 1 49 



Kostychev and M. Afanassjewa show that the agents of lactic 

 acid fermentation, Bac. caucasicus and Bacterium lactis acidi 

 Leichmann, which ferment sugar to lactic acid without forming 

 by-products, do not form the slightest trace of carbon dioxide 

 with unrestricted aeration. Hence they are wholly incapable of 

 respiration. It is to be observed that these bacteria, which 

 belong in the category of facultative anaerobes, cause the 

 fermentation of much larger amounts of sugar per unit of dry 

 substance than does yeast, which is only a temporarily anaero- 

 bic fungus and which cannot exist for an indefinite period 

 without access to the air. 



