27 



dissolved more or less of the iiie]n])rancs. In the summer tracheids 

 the iuim])er of fissures in the walls is ver^^ larg-e. They all extend 

 diagonally across the tracheids as in the spring- cells, and wherever a 

 hole occurs there two fissures seem to cross. The smaller fissures 

 have no counterpai't in the secondary lamella of neighboring cells as 

 a rule, showing the complete independence of the two halves of the 

 cell wall. The margins of the fissures are ragged, and the fissures 

 themselves are very irregular in shape, and look as if they had been 

 formed suddenly. The wood substance itself has been changed com- 

 pletely. With phloroglucin and hydrochloric acid it stains red, and 

 when the wood, finel}" powdered, is extracted with absolute alcohol 

 quantities of hadromal are obtained. No reaction for cellulose can be 

 obtained, and it seems as if the latter has been completely destroyed. 

 An aqueous solution yields several compounds — an amorphous sub- 

 stance, possibly a humus compound; a faint trace of some sugar, as 

 shown by the phenylhydrazine test; and small quantities of citric and 

 succinic acids. These are doubtless all decomposition products. 

 There is also some compound present which reduces Fehling's solu- 

 tion vigorously. After the walls of the tracheids are filled with holes 

 and fissures they have reached the last stage of decomposition. A 

 touch will then cause them to fall into many pieces. When boiled in 

 water, the walls swell somewhat, and a pasty mass results when 

 squeezed. With dilute KOH the walls swell to three times their size, 

 and portions of them dissolve completely. 



The formation of the sheets of mycelium seems to take place in one 

 of two ways. In one case the hyphaj in the white areas mentioned 

 above exert a solvent action on the walls. This first becomes evident 

 in the cells of the medullary rays. Their walls disappear completely, 

 and the spaces are rapidly filled by the growing mycelium. The walls 

 of the wood cells adjoining the medullary ra3^s are attacked, possibly 

 at the same time. The secondar}^ lamella* shrink and finally disappear 

 altogether, leaving a fine framework of the primary lamella. This 

 framework is usually broken in hundreds of places, and as a result 

 only pieces of the walls remain em])edded in a web of h3'pha?. The 

 })ordered pits are destroyed from within outward, the torus resisting 

 longest (PI. X, fig. 5). The latter is often freed and can be seen lying 

 free in the cell. The triangular areas (as seen in cross section) of the 

 primary lamella, formed where several cells join, are the last to dis- 

 appear. A hole is thus formed which is completely filled with myce- 

 lium. The latter spreads from this point in several directions. The 

 writer is of the opinion that very little actual solution of the wood 

 takes place, resulting in the fornuition of holes or cavities. Hero and 

 there it doul)tless does occur, but rather as the exception, and possibly 

 in the early stages of the development of the mycelium. It seems 

 very much more prol)ab1(* that the socond mode is the usual o!ie. As 



