66 Cellulose 



In the second group of resolutions, constituting ' decay,' 

 various micro-organisms play an important part. The extreme 

 resolution takes place according to the equation 

 C 6 H 10 5 + H 2 = 3 C0 2 + 3 CH 4 



(Hoppe-Seyler, Ztschr. Biol. 10, 401). This decomposition 

 is determined by the amylobactermm, and may be taken as 

 typical. Pure * fermentations ' of cellulose have, however, 

 been but little investigated. 



In the decay of plant structures we have to deal with a 

 complex of compounds and with celluloses of very various 

 character. Again, therefore, we can only treat of these 

 processes in their broad and general features. These are, in 

 the main, (i) complete resolution, of the kind described and 

 formulated above : (2) a tendency in the precisely opposite 

 direction, i.e. towards condensation of the carbon nuclei to 

 still more complicated forms, accompanied by the splitting off 

 of water. These processes are concurrent as they are in the 

 decompositions by heat, about to be described. As visible and 

 tangible results of this tendency to carbon accumulation we 

 have the vast aggregations of peat, lignite, and coal in all its 

 forms in the earth's crust, which are the residues of the flora 

 of a past geological age. In the coal measures, moreover, 

 there is abundance of gaseous carbon compounds also stored 

 tip. These being chiefly marsh gas and carbonic acid, the 

 process of coal formation, in its earlier stages, appears to have 

 been similar in all respects to those which we can observe 

 around us as attending the decay of vegetable matter in the 

 mass. 



These decompositions are necessarily of a complex character, 

 and are, no doubt, largely dependent upon the presence of nitro- 

 genous substances. We may cite in illustration the disintegration 

 of leaf parenchyma in the well known process of * skeletonising.' 

 Leaves of the poplar, pear, &c. are covered with water and set aside 



