Tlie Blacl- Zones Formed bij Wood-Destroying Fungi 45 



aud a^jpearing as a blackish zoiiej the wood gum, iu its par- 

 tially oxidized state, apparently is the substance which is re- 

 sponsible for most of the discoloration. Later, however, when 

 the blackish zones advance and the decay becomes completed 

 within that portion of ^\■ood which the decomposition products 

 formerly occupied, the wood no longer responds to chemical 

 tests for wood gum. 



11. By the action of a strong oxidizing reagent on fresh 

 sapwood a brown decomposition product can be prepared 

 artificially which is essentially like that occurring naturally 

 in dicotyledonous woods, whether in wounded areas of living 

 trees, dead wood, or as the result of the action of wood- 

 destroying fungi. 



12. After subjecting both sound aud intiltrated wood to 

 the action of a strong oxiding reagent and extracting tbe 

 products whose nature w^as changed by the action, the chem- 

 ical properties of the respective extracts indicate that they 

 are, for the greater part, made up of like substances. In the 

 case of the infiltrated w^ood in addition to the materials orig- 

 inally present in the sound wood there is present one or more 

 decomposition products which are temporarily left little or 

 not at all affected by the fungus producing the decomposition. 

 The solubility relations of the extracts obtained from both 

 woods indicate that, before oxidation, they would be classed 

 with the hemicelluloses but that they become greatly altered 

 in nature by the action of the oxidizing reagents. 



13. The decomposition products whose formation is due to 

 the action of wood-destroying fungi have proven to be a group 

 of substances analogous to or nearly identical with the decom- 

 position products which arise under certain circumstances in 

 dead wood that is entirely free from fungous attack and which 

 have been known under the name " wound gum." Their 

 fonuation is greatly accelerated by the presence of wood- 

 destroying fungi which greatly hasten the decomposition and 

 hence the oxidation. 



