THE METABOLISM OF PLANTS. 2OQ 



Nor is alcoholic fermentation confined to Fungi. Be"rard 

 pointed out as long ago as 1821 that ripe fruits continue 

 to exhale carbon dioxide in an atmosphere destitute of 

 oxygen, and that this is accompanied by a diminution 

 of the sugar contained in them. Lechartier and Bellamy, 

 as well as Pasteur, have since shewn that the exhalation of 

 carbon dioxide and the disappearance of sugar is accompanied 

 by a formation of alcohol, that the phenomenon is in fact 

 one of alcoholic fermentation. More recently Brefeld and 

 de Luca have obtained the same results in experiments with 

 fruits, seeds, leaves and branches. 



Nor is the alcoholic fermentation the only fermentative 

 process which is induced by the absence of oxygen. So far 

 as we know the conditions of the butyric fermentation, the 

 lactic fermentation, and of the putrid fermentation, fermen- 

 tations which are effected by certain Schizomycetes, they 

 only take place in the absence of oxygen. It would ap- 

 pear that similar processes may be induced in the cells of 

 any organ. Thus Boehm and de Luca have shewn that if 

 any part of a living plant be insufficiently supplied with 

 oxygen (in these experiments, by keeping it immersed in 

 a limited quantity of water), hydrogen is sooner or later 

 evolved, and, in the case of aquatic plants, marsh gas (CH 4 ), 

 at a later period. Boussingault observed that leaves and 

 branches evolve combustible gas under these conditions, and 

 Schulz found that when seeds germinated in sealed glass 

 tubes, considerable quantities of hydrogen were given off. 

 Further, an evolution of hydrogen has been observed when 

 parts of plants which contain mannite (C 6 H 14 O 6 ), e.g. various 

 Agarics (Miintz), leaves, flowers, and unripe fruits of the 

 Olive, leaves of the Privet (de Luca), are deprived of free 

 oxygen. There can be little doubt that this evolution of 

 hydrogen is accompanied by a diminished formation of 

 watery vapour. 



Lactic acid and all substances capable of undergoing lactic fermenta- 

 tion (sugars, starch, many of the more complex organic acids, proteids) 

 are decomposed in such a way as to give rise to butyric acid, carbon 

 dioxide and hydrogen being given off, thus : 



V. I4 



