44 College of Forestry 



5. The blackish zones are not constant in position since the 

 decomposition products, which cause the discoloration, move 

 forward with the advance of the decay in any part of the 

 stem and ultimately disappear upon its comj^letion within that 

 part. The continual occurrence of the blackish zones between 

 decayed and undecayed wood is due to the fact that the de- 

 composition products are destroyed together with the wood 

 while new ones are foraied constantly from the wood as fast 

 as it is attacked by the advancing fungus. 



6. In the decay of coniferous woods the formation of de- 

 composition products of similar nature to those studied here 

 is very small in quantity as compared wdth those arising in 

 the decay of dicotyledonous woods. 



7. The formation of the brown decomposition products is 

 dependent mainly upon the concurrence of tliree factors: (a) 

 the presence of dead cells, (b) an optimum supply of mois- 

 ture, and (c) a supply of oxygen sufficient to promote 

 oxidation. 



8. The partially decomposed material of woody plants 

 forms a particularly vague and indefinite group of substances 

 containing all the non-volatile products of fungal, enzymic, 

 and oxidative actions on the plant residues. The resultant 

 products are exceptionally resistant to chemical reagents. 



9. It is evident that the cell contents and certain other 

 substances, particularly the hemicellulose xylan (wood g'um), 

 that originally were combined with the cellulose to constitute 

 the cell wall furnish the formative material which, through 

 oxidation upon the entrance of air and the presence of water, 

 coagulates to thick drops and gives rise to the decomposition 

 products which ultimately infiltrate certain portions of the 

 wood, causing them to appear as blackish zones. 



10. In the wood of the pignut hickoTv the hemicellulose 

 xylan (wood gum) is destroyed early in the grogress of the 

 decay. In the early stages of the decomposition of the wood 

 (in that portion infiltrated wnth the decomposition products 



