28 CoJlefje of Forestry 



pendent upon atmospheric oxygen, lieat, and water in certain 

 proportions. According- to Bailey the optinuim conditions 

 for sap-staining are found in green timber during hot humid 

 weather, whereas unfavorable conditions are found in cold 

 dry weather and in logs immersed in water. 



It is generally known that if fungous-infected wood be 

 exposed to the air for several hours its surfaces turn brown. 

 This is especially striking in woods that normally are white, 

 Lindroth (lOO-t) has made obser\'ation& of this nature on 

 sections of birch wood decayed by Pohjporus nigricans Fries. 

 He marked the outer limit of a dark zone on a section with a 

 lead pencil and after keeping the wood in a moist chamber 

 for 15 hours observed that a new discolored zone had formed 

 outside of the pencil mark. He concluded therefore that the 

 formation of this new discolored zone occurred through the 

 combined action of the atmospheric oxygen and the fungus. 

 That the oxygen alone did not cause this is obvious because 

 sound birch wood does not become colored so rapidly when 

 exposed to the air under the above conditions. That, on the 

 other hand, the fungus alone did not cause the new discolora- 

 tion he confirmed since the dark zone could only be found 

 within a few millimeters of the exposed surface. 



As Miinch (1910-) correctly stated, the formation of the 

 brown decomposition product is dependent npon the concur- 

 rence of three factors, the presence of dead cells, an optimum 

 supply of moisture, and a sufficient supply of oxygen to pro- 

 mote oxidation. This makes it clear why the so-called pro- 

 tection wood formation is often confined to a very definite 

 zone, namely directly at the Ixiundary between dead and liv- 

 ing wood." In Miinch's opinion it would be far more con- 



^ In addition to the above-described formation of the decomposition 

 products resulting from the oxidation of the cell contents Miinch (1910-) 

 observed that the mycelium of certain fungi excreted drops of a sub- 

 stance which, upon microscopic examination and microchemical tests, 

 apparently was identical with that arising in the parenchj'ma cells of 



