168 TIMBER AND SOME OF ITS DISEASES. [CHAP. 



to be filled with the fungus filaments, and look like 

 long white streaks in longitudinal sections of the 

 wood showing as white dots in transverse sections. 



It is not necessary to dwell on the details of the 

 histology of the diseased timber : the ultimate fila- 

 ments of the fungus penetrate the walls of all the 

 cells and vessels, dissolve and destroy the starch in 

 the medullary rays, and convert the lignified walls of 

 the wood elements back again into cellulose. This 

 evidently occurs by some solvent action, and is due to 

 a ferment excreted from the fungus filaments, and the 

 destroyed timber becomes reduced to a brown mass 

 of powder. 



I cannot leave this subject without referring to a 

 remarkably interesting specimen in the Munich 

 Museum. This is a block of wood containing an 

 enormous irregularly spheroidal mass of the white 

 felted mycelium of this fungus, Polyporus sulphureus. 

 The mass has been cut clean across, and the section 

 exposes a number of thin brown ovoid bodies em- 

 bedded in the closely-woven felt : these bodies are of 

 the size and shape of acorns, but are simply hollow 

 shells filled with the same felt-like mycelium as that 

 in which they are embedded. They are cut in all 

 directions, and so appear as circles in some cases. 

 These bodies are, in fact, the outer shells of so many 



