33 



a long-er hole. The holes are never sharply defined, for there is always 

 more or less of a white mass of metamorphosed fibers which remain 

 in position next to the unchanged wood, and in many cases the whole 

 area is thus occupied, and one can recognize the change only by the 

 white color. In older holes this lining- is often replaced by felts of 

 brown mycelium (PI. X, fig. 3) which partially or completely fill the 

 cavity. The lameihe of wood between the holes ultimatel}^ become 

 of an ahnost uniform thickness (PI. X, fig. 3), and on cross section 

 show one or more black lines which extend completely around each 

 cavity at an equal distance from the walls of two adjoining cavities. 

 These black lines begin to appear at a stage intermediate ])etween that 

 shown in fig. 2 and fig. 3 of PI. X. They are of variable width and 

 grow darker and more marked as the decomposition advances. A lon- 

 gitudinal section shows that they extend around the holes in a vertical 

 direction also; in other words, a thin hwer of dark-brown matter sur- 

 rounds the individual cavities. A closer examination shows that the 

 brown lines are due to masses of dark-brown hvpha3 which fill each 

 separate wood cell so completely as to plug it entirely. The hyphte 

 are closely matted together and are incrusted with a brown substance 

 which dissolves in part in dilute KOH and entirely in warm nitric 

 acid. These hyphal plugs occur in every tracheid surrounding a hole 

 and fill it for a shorter or longer distance. The plugs of adjacent cells 

 may be continuous, or may follow one another much as a series of 

 steps. This is shown in PI. IX, figs. 10 and 13. The latter represents 

 a radial view of a number of tracheids at one side of a hole. The parts 

 of the tracheids toward the hole (t) are completely changed to white 

 cellulose fibers, while the parts on the other side of the plug (l) give 

 lignin reaction. The brown hypha? fill the wood between the holes 

 rather loosely, and it is only when about half way between two cavi- 

 ties that they become matted together so as to form the plugs. The 

 brown incrusting substances occur in or on the cell walls in the imme- 

 diate neigh))orhood of the holes, and the manner of occurrence leads 

 one to suspect that they were deposited in liquid form, for they have 

 difiused through the various cells in all directions from the wall of the 

 cavities. 



The changes in the cell walls which result when the mycelium 

 attacks them are practically those so fully described l)y Hartig.^ 

 There is a gradual extraction of those elements which give the 

 so-called lignin reaction, the hadromal of Czapek. This begins in the 

 tertiary lamella tuid proceeds outward slowly through the secondary 

 lamella. The primary lamella at this period splits in the middle and 

 is shortly after dissolved, leaving the individual tracheids entirely free 

 from one another, each composed of approximately pure cellulose. 



' Ilartijr, Robert. Zersetzungsersclieinungen des Holzes, etc. 32. 

 577«j— No. 2.5 3 



