33 



a lono-er li()l(\ The holes arc never sharply defined, for there is alwa3^s 

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

 in position next to the unchanged wood, and in man}^ cases the whole 

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

 white color. In oldc^r holes this lining is often replaci^d by felts of 

 brown mycelium (PL X, fig. 8) which partially or completel}' till the 

 cavit}^ The lamelhe of wood between the holes ultimately become 

 of an almost uniform thickness (PI. X, fig. 8), and on cross section 

 show one or mon^ l^lack lines which extend completely around each 

 cavit}^ at an equal distance from the walls of two adjoining cavities. 

 These black lines })egin to appear at a stage intermediate between that 

 shown in fig. '2 and fig. 3 of PL 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 layer of dark-brown matter sur- 

 rounds the individual cavities. A closer examination shows that the 

 brown lines are due to masses of dark-brown h^^phae which fill each 

 separate wood cell so completely as to plug it entireh\ The hyphae 

 are closely uiatted together and are incrusted with a brown substance 

 which dissolves in part in dilute K.OH and entireh" in warm nitric 

 acid. These h3^phal 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 ma}" follow one another much as a series of 

 steps. This is shown in PL 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 completeh" changed to white 

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

 lignin reaction. The brown hyphge fill the wood between the holes 

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

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

 ])rown incrusting substances occur in or on the cell walls in the imme- 

 diate neighborhood of the holes, and the manner of occurrence leads 

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

 dift'used 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 by 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 and 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. 



^ Hartig, Robert. Zersetzungserscheinimgen den Holzei?, etc. 32. 

 577G— No. 25 3 



