32 College of Forestry 



As Miinch (1910^) states, it is therefore clear that an import- 

 ant accumulation of materials occurs, especially in those places 

 where the drying is gTadual or where the penetration of the 

 disease-producing organism is very slow as, for example, in 

 the periphery of the decayed areas. Here the wood cells have 

 the maximum time to attract material to them before they in 

 turn become attacked and killed by the fungal secretions or 

 other injurious influences. It is not impossible that even after 

 death a woody portion may be enriched by the flow of sub- 

 stances from the suiTOunding, living cells due to purely 

 physical causes and, upon the concentration of such sub- 

 stances the deposition of them as solid materials may occur 

 within the areas concerned. Otherwise the frequently 

 described accumulations of calcium carbonate and calcium 

 oxalate in plant tissues would be difiicult to explain. How- 

 ever, this is to be regarded as a hypothesis less well estab-- 

 lished. 



Such increase of sul)stance as a result of pathological heart- 

 wood formation has been investigated by numerous workers. 

 Lindroth (1001) stated that the infiltrated decomposition 

 ]iroducts formed in birch wood, as a result of its decay by 

 Polyponis nigricans Fries, imparts great hardness to the wood 

 and retards the decomposition of the same. He stated that 

 while the specific gravity of the sound w^ood was 0.99, that 

 of the dark infiltrated zone was 1.23. Ijy absolute dry weight 

 he found the specific gTavity of the sound wood was 0.77 

 while that of the dark zone was 0.90. 



THE PHYSIOLOGIC SIGKIFICAXCE OF THE I)E- 

 CO:\fPOSITION PRODTTCTS. 



Many investigators have observed that the fungal hyphae 

 <lo not appear to be able to penetrate the heavier infiltrations 

 of decomposition products occurring as blackish zones de- 

 marking decayed from undecayed areas of wood. Conse- 

 quently they have attriluited a protective efi^ect to this forma- 



