Tlie Blacli Zones Formed hy Wood-Destroymg Fungi 19 



as follows. In the vicinity of the margins of wonnds a red- 

 dish discoloration was observed after 8 to 10 days. This is 

 dne to a' coloration of the cell walls, especially those of the 

 pith rays. In these cells Ijrown dro])s (the wonnd gnm) 

 arise as a new formation of the cell contents and partly as a 

 transfonnation of the starch grains. Their formation then 

 continues farther. The brO'wn substance infiltrates the cell 

 walls and eventually exudes into the kimina of the vessels, 

 partly occluding tihem. From this description it does not 

 appear that Frank's view is justified for, as Miinch (1910") 

 has stated, a " browned " tissue, the parenchyma cells of 

 which are filled with brown material, is necessarily dead and 

 therefore incapable of further vital activity. In such tissue 

 described by Frank, if the formation of the brown substance 

 continues, then it can hardly be a question of a secretion of 

 living cells. 



It is difiicult to understand how anyone can consider such 

 changed and discolored cells to be alive. The investigations 

 of Bohm, Ii. IJartig, von Tubeuf, and later those of Miinch 

 (1910") have shown, beyond all possible doubt, that the cells 

 furnishing the decomposition products are always dead. 

 j\Iiinch found that the formation of the brown product 

 occurred in dessicated cells as well as those infected by fungal 

 hyphae — cells which were unquestionably dead. 



There is no further foundation for asserting that the de- 

 composition products arise from living parenchyma cells 

 other than the following account of Frank (1884, p. 330) in 

 which he states that the g-um fonnation as well as the forma- 

 tion of tyloses is truly a vital process and not a purely chemi- 

 cal process of disintegration. This follows from the fact that 

 it does not occur in fallen trees and branches as soon as they 

 are dead. Miinch (1910^) declares this to be Avrong and 

 states that under certain circumstances there arises in fallen, 

 doubtlessly dead, woody parts a brown material which, 

 according to its appearance, origin, and chemical reactions, 



