504 FERMENTATION. 



On fine days in the open the light is not seen, but as soon as these structures are 

 brought into a dark room, the phenomenon of light is to be seen, even during the 

 day. The luminosity of the night is not increased by sun-illumination during the 

 day, and consequently the phenomenon has nothing in common with that pecuhar 

 phosphorescence exhibited during the night by fluor-spar, which has previously 

 been exposed to sunhght. 



There are certain organic substances which shine in alkaline solutions when 

 oxygen is present. It seems natural to suppose that such materials are formed in 

 the agarics mentioned, and that oxygen is conveyed to them in respiration, thus 

 producing the phenomenon of light. At any rate this would be the simplest way 

 of explaining the luminosity. As to the advantage accruing to the plant itself, we 

 can only form surmises. It seems most probable that the fungus-flies and beetles 

 which deposit their eggs in the mycelia and fructifications of Hymenomycetes, 

 and which are connected with the distribution of their spores in a manner to be 

 described in detail later, are thereby guided to the fungi in the dark of night. 

 Many of these flies and beetles only fly at night, and, like so many winged 

 nocturnal animals, direct their path towards a luminous object. It may be, there- 

 fore, that the light proceeding from the agarics cited serves as an allurement and 

 guide to the night-flying insects, just as the odour and brilliant colouring of other 

 Hymenomycetes attracts the fungus-flies and beetles which swarm in broad day- 

 light. 



FERMENTATION. 



About thirty years ago the difference between plants and animals was formu- 

 lated as follows: — Plants transform kinetic into potential energy, and form organic 

 compounds by the reduction of inorganic food, especially from carbonic acid, nitric 

 acid, and water; animals transform potential into kinetic energy, and decompose 

 and bum by respiration the organic compounds, formed by green plants, which 

 serve them as food. This distinction, however, only holds good in part. On the 

 one hand, plants devoid of chlorophyll are not taken into consideration, and on 

 the other, it has been established that green plants also breathe, and therefore 

 transform potential into kinetic energy. The respiration of plants does not differ 

 either in its method or in its object and significance from that of animals. In both 

 cases the living protoplasm withdraws oxygen from the air in order to convey it 

 to certain expressly prepared carbon compounds which have been rendered com- 

 bustible, and in both cases these carbon compounds are burnt in order that the 

 necessary impelling forces may be obtained for further life and growth. But the 

 analogy between plants and animals holds still further in this respect. When 

 animals which are tenacious of life, e.g. frogs, are placed in an atmosphere contain- 

 ing no oxygen, they do not immediately perish, and do not at once cease to exhale 

 carbon dioxide, consequently they still convert a certain amount of potential 

 energy for a short time, by the combustion of carbon compounds in their bodies. 

 They cannot derive the oxygen necessary for this from the surrounding air; there 



