2G College of Forestry 



naturally expect to have an increased flow of air through the 

 wood, thcrehv permitting' a much more rapid and coinpleto 

 decomposition than could possibly occur in coniferous woods. 



In order to be entirely certain that the decomposition 

 product is. produced in cells that are attacked by wood-destroy- 

 ing fungi, Miinch conducted an experiment in which he 

 placed pieces of fresh beech sapwood in closed sterilized 

 chambers and observed them for several weeks. He noticed 

 that these Avood samples developed tyloses profusely; in the 

 cambium region even a luxuriant growth of callus began. 

 However, the familiar brown coloration betraying the forma- 

 tion of the decomposition products did not appear, the sur- 

 face of the wood merely coloring to a pale yellowish brown. 

 If, on the contrary-, the pieces of wood were inoculated with 

 a wood-destroying fungus the discoloration, indicative of the 

 decomposition of the cell contents into a brown substance, 

 arose immediately in all parts killed by the fungus. There 

 can therefore be no doubt that the brown drops, designated 

 by Frank as wound gum, are a decomposition product of the 

 cell contents and that they occur only in dead cells. 



The striking fact that the cell contents, which are without 

 question very easily oxidized, do not experience oxidation in 

 the cells even where there is a free transmission of air 

 through the wood is to be explained by the properties of the 

 living protoplasm. With the death of the protoplasm by dry- 

 ing, frost, heat, fungous attack, etc., its permeability is 

 destroyed. As a result the air flows in upon the vacuole con- 

 tents which are no longer protected and oxidation of the cell 

 contents occurs. 



The j)resence of moisture is as necessary to the oxidation 

 described as it is for most chemical decompositions of that 

 nature. According to Miinch, in the case of the poplar twigs 

 for example, if the dessication be greatly hastened by remov- 

 ing the bark and drying in a hot room, no browning occurs. 

 In this case, after the death of the protoplasm by dessication, 



