Decomposition ot Ligniiis 121 



Table 'ii. CiiANtiES in" the Chemral C().MrusiTio,\ of Wood as a Result oe Its 

 Decomposition (from Rose and Lissc) 



On basis of dry wood. 



for example, lost all or nearly all of its cellulose constituents, but 

 still contained 85.55 per cent lignin, after considerable decomposition. 



W^hen plants are attacked by soil microorganisms, the lignins are 

 aflPected only to a very limited extent, especially when present in 

 mature plants and under anaerobic conditions of decomposition. As 

 a result, lignin contributes considerably to the formation of humus 

 in soils, in composts, and in certain types of peat bogs. 



Under aerobic conditions, lignin is not absolutely resistant to de- 

 composition but can be gradually oxidized. The exact nature of the 

 organisms concerned in the oxidation of the lignins in soils and the 

 nature of the products formed are not yet clearly understood. It is 

 known, however, that certain organisms, like some of the higher or 

 fleshy fungi, including some of the wood-destroying forms, are 

 capable of attacking lignins very rapidly. Falck distinguished two 

 processes in the decomposition of wood by fungi, namely, "destruc- 

 tion" and "corrosion." In "destruction," cellulose is decomposed, 

 whereas the lignin accumulates; organisms like Merulius lacnjmans 

 and species of Coniophora, Poria, and Lenzites are concerned in this 

 process. In "corrosion," the lignin as well as the cellulose is at- 

 tacked. Polyponts annosus is responsible for this process in spruce 

 wood. Tramc'tes pint attacks the lignin in pine wood. In the "de- 

 struction" of wood, the cellulose diminished from 56 per cent in the 

 original material to 7.8 per cent, whereas the lignin increased from 

 23.5 to 56.5 per cent; in "corrosion," the lignin diminished from 23.5 

 to 15.1 per cent and the cellulose from 56.0 to 48.2 per cent. Several 

 other fungi, like Stereum rugosum, are also capable of attacking lig- 

 nins. Agaricus nebitlaris destroys lignin, cellulose, and pentosan, 

 whereas Coniophora ccrehella is able to decompose cellulose but not 

 lignin. 



The common edible mushroom, Fsalliota campestris, is capable of 

 utilizing lignin for its nutrition. In 51 days, 18 per cent of the lignin 



