Tlie Black Zones Formed by W ood-Dest7'oying Fungi 15 



and dead wood. Even before Bolim, Tlieodor Hartig (1857) 

 and others had concerned themselves with the most important 

 phenomena of normal and pathologic heartwood formation as 

 well as the chemical reactions of the infiltrating decomposi- 

 tion products. 



Gaunersdorfer (1882) likewise contributed to this subject. 

 He studied (principally on Syringa) a brown zone of pro- 

 tection wood in wounded twigs, established its similarity to 

 normal heartwood, and made a careful examination of the 

 brown infiltration. His results indicate a noticeable increase 

 in weight for the pathologic heartwood. The physiologic 

 significance of the protection wood is to retard or render im- 

 possible the harmful atmospheric inflow into the deeper-lying 

 living tissue. It would seem, therefore, that the protection 

 Avood has an important function to fulfill. He assumed that 

 the infiltrating substance is produced from living cells, chiefly 

 from the starch grains. He, as well as Bohm, believed that 

 the occlusion of w^ounds by the infiltration of the wood con- 

 stitutes a safeguard against injurious external atmospheric 

 influences. 



Opposed to this von Tubeuf (1886) found in Cytisus that 

 wood transformed to pathologic heai'tA\-ood is easily pene- 

 trated and destroyed by fungal threads. Therefore he con- 

 tested the idea that a protection is instituted against destruc- 

 tion and stated that the transformation of the margin of the 

 wound to pathologic heartwood did not render the artificial 

 closing of the wound unnecessary as had been claimed by the 

 earlier authors. For the remainder von Tubeuf leaned 

 toward Bohm's theory. In his opinion pathologic heartwood 

 formation, subsequent to wounding, is a reaction against 

 oxidation and pressure changes and, in specific cases, perhaps 

 against fungal ferments. He confirmed R. Hartig's observa- 

 tion that all pathologic heartwood cells are dead.'^ 



* Further literature, the discussion of whicli would take too long, is 

 given by von Tubeuf ( 1899) . 



