DECAY OF WOODY FIBRE. 45 



they take up their nourishment, and compare its 

 composition with that of the vegetable substances 

 which compose their structure. 

 * All these questions will now be examined and 

 discussed. It has been already shown, that the 

 carbon of plants is derived from the atmosphere : 

 it still remains for us to inquire, what power is ex- 

 erted on vegetation by the humus of the soil and 

 the inorganic constituents of plants, and also to 

 trace the sources of their nitrogen. 



ON THE ORIGIN AND ACTION OF HUMUS. 



It will be shown in the second part of this work, 

 that all plants and vegetable structures undergo 

 two processes of decomposition after death. One 

 of these is named fermentation, the other decay, 

 putrefaction, or eremacausis* : . 



It will likewise be shown, that decay is a slow 

 process of combustion, a process, therefore, in 

 which the combustible parts of a plant unite with 

 the oxygen of the atmosphere. 



The decay of woody fibre (the principal consti- 

 tuent of all plants) is accompanied by a pheno- 

 menon of a peculiar kind. This substance, in 

 contact with air or oxygen gas, converts the latter 

 into an equal volume of carbonic acid, and its decay 



* The word eremacausis was proposed by the author some time since, 

 in order to explain the true nature of putrefaction ; it is compounded 

 from -/jpe'jua alow and Kav<ns combustion. 



