The Black Z<))ics Formed hy Wood-Deslnnjing Fiuigi 43 



tioii. The similarities of tlie substances decomposed bv the 

 oxidizing- treatment, as regards solubility and behavior toward 

 other reagents except the oxidizing reagent, show relationship 

 between the original materials and the decomposition products 

 here in question. The solubility relations of both indicate 

 that, before oxidation, they would be classed with the hemi- 

 celluloses, l>ut that they are so altered by oxidation as to 

 become soluble, particularly in alcohol aiid acetone Avithout 

 losing their insolubility in sodium hydroxide and in acidulous 

 salt solutions. 



SUMMARY. 



1. The brown substance commonly occurring in dicotyle- 

 donous woods attacked by wood-destroying fungi is indica- 

 tive of the first stage of the decomposition of the wood. 



2. The formation of a similar and probal)ly identical sub- 

 stance also occurs in wounds of living dicotyledonous trees 

 and, under certain circumstances, in fallen woody parts 

 where fungous growth may not Ix^ present. This is to be con- 

 sideired as due solely to oxidation of the woody sul^stancc 

 without the stimulus afforded by the presence of wood- 

 destroying fungi which would greatly hasten the decom- 

 position. 



3. Both decomposition ]:)roducts arise only after the death 

 of the cells through the oxidation of their contents and cer- 

 tain constituents of their walls. This fonnation occurs most 

 notably in the parenchyma cells. 



4. The decomposition products formed in the decay of 

 dicotyledonous woods infiltrate the cell walls to a greater or 

 less extent, frequently becoming so abundant as to form 

 numerous brown drops wdthin the lumina of the cells. Such 

 deposits appear in the wood as blackish zones of varying 

 thickness which occur at first between decayed and undecayed 

 areas and later separate areas in different stages of decay. 

 Wood thus infiltrated is to be considered as pathologic heart- 

 wood. 



