RESPIRATION AND OXYGEN. 95 



FUNGI. 



Humboldt (1793) was the first to state that agarics gave off hydro- 

 gen during respiration, and DeCandolle (1832) later determined that 

 Sphceria and Peziza exhaled hydrogen when exposed under water 

 to sunlight. 



Marcet (1829, 1834) found that fungi excreted a small quantity 

 of C0 2 , but no hydrogen, in bell-glasses containing air. When 

 placed under water, however, they rapidly disengaged both nitro- 

 gen and hydrogen in sunlight as well as in darkness. In his later 

 experiments the respiration of fungi was studied in the air, in oxygen, 

 and in nitrogen. In every case a certain amount of C0 2 was ob- 

 tained, abundantly in the case of oxygen and less so in that of nitro- 

 gen. In these experiments no generation of hydrogen occurred, and, 

 contrary to his preceding opinion, he admitted that the hydrogen 

 was produced by the beginning of decomposition. 



Pasteur (1861, 1876) was the first to show that yeast and certain 

 bacteria could grow in the absence of oxygen if a supply of energy 

 was available, but that anaerobic growth was not indefinitely pos- 

 sible, in the case of yeast at least. 



Brefeld (1874, 1876) found that yeast was still capable of develop- 

 ment in an atmosphere of CO 2 which contained one six-thousandth 

 part of oxygen. Yeast was shown to possess the ability to grow 

 without free oxygen in the midst of sugars, which were fermented to 

 CO 2 and alcohol. The limit of growth occurred at 12 per cent and 

 that of fermentation at 14 per cent of alcohol. A similar ability was 

 exhibited by Mucor racemosus, but the fermentation proceeded more 

 slowly under similar conditions, and the respective limits of growth 

 and fermentation were 4.5 and 5.5 per cent of alcohol. In the case 

 of Mucor stolonifer the fungus produced fermentation without grow- 

 ing and became inactive at 1.5 per cent of alcohol. He concluded 

 that in the case of all plants, from the simplest to the highest, ab- 

 normal decompositions occur in the absence of oxygen, which, in 

 certain respects, such as the constant formation of C0 2 and alcohol, 

 are in harmony with the alcoholic fermentation of yeast. 



Selmi (1874) observed the evolution of hydrogen from molds and 

 from Agaricus ccesarea and supposed that this occurred also in the 

 presence of free oxygen. Gugini (1876 : 1 1 1) pointed out that this was 

 due to the use of sulphur or arsenic in the experiment, while Missaghi 

 (1875) found no hydrogen when moulds grew in atmospheric air. 



Miintz (1876 : 67) determined that Agaricus campestris produced 

 no hydrogen in atmospheric air constantly renewed. When, how- 

 ever, this mushroom was placed in an atmosphere without oxygen, 

 it produced a small quantity of hydrogen, as well as large amounts of 

 CO 2 . He stated that all fungi in an atmosphere without oxygen 

 transform the sugars which they contain into alcohol and CO. 



