47 



stitute the white spots and also the white ))aiKls spoken of. The 

 various steps leading to the complete separation of thc^ cellulose fibers 

 are exactly those which have been described for a similar process 

 caused by the hyph^e of Trametes j;m^' 

 forma ahictis. 



A very different change is going on at 

 the same time in the spring wood, and 

 gradually spreads from this to the sum- 

 mer wood. This change may be likened 

 to the one which Hartig has described as 

 taking place in pine wood attacked l)y 

 Polypofiis IxrrcaJi^} The hypha3 of the 

 fungus develop in the wood cells with 

 great rapidity, hlUng them completely. 

 Nimierous hyphi\i pass through the walls 

 in all directions, making large irregular 

 holes many times the diameter of the 

 hyphje which pass through them. The 

 secondary walls of the wood cells are 

 gradually dissolved; a faint granular 

 appearance of the walls is seen at first, 

 and little by little the walls become thin- 

 ner. At last only the primar}^ lamella is 

 left, and in the bordered pits the torus 

 (PL XI, fig. 3). The whole wall finally 

 disappears, leaving simply that part of 

 the wall belonging to two or three cells, 

 namely, the portion having a triangular 

 cross section. This solution of the walls 

 goes on simultaneousl}^ throughout large 

 areas. The medullary rays disappear 

 complete h^, long before the wood cells are 

 entirely gone. The spaces left by the 

 dissolved cells are rapidly filled with 

 hyphae and these hold portions of the cell 

 walls not yet destroyed in place, and 

 give consistency to the mass, which thus 

 retains the shape of the wood before the 

 attack. The whole mass can be compressed by slight pressure and 

 will not return to its original size. This accounts for the extremely 

 light weight of wood thus decayed. In PL XI, fig. 2, a radial view 

 of wood in an advanced stage of decay is shown. The straight black 

 lines indicate groups of wood vessels, two or more; the hyphse between 



Fig 



Base of spruce branch, showing 

 its resistance to the attack of tlie my- 

 celium of Polyporus subacidu)< Pk. 



Hartig, R. ZerHetzAingseri^cheinungeii de^ Holzes, etc. 



