442 



BASIDIOMYCETES. 



rays appear snowy white at the place where the two forms 

 of rot meet ; this is due to an accumulation of starch left 

 after the cell-walls have been almost completely dissolved. 



Polyporus (Poria) vaporarius (Pers.) l (Britain and U.S. 

 America). The sporophores are white, and have a pungent 

 odour ; they form crusts (never brackets) closely adherent to 

 dead substrata, especially to beams and other timber in buildings, 





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 ft, 



i fr# 

 1 : : lrfl 



i s , i .. _, y-> " % 



5 ; " ! .--," ^'. ,, 

 I '' - a^'l 

 f ;V ,,- ,t* ..>i; a^j^V^ 

 i.::'' ; , -: If-'i 



Fin. 273. Polyporus dryadeus. Later 

 stage of decay of Oak-wood. The darker 

 places still consist of firm brown wood ; 

 the white, however,' are soft cellulose. 

 (v. Tubeuf phot.) 



Fin. 274. Polyporus dryadeus and Polii- 

 porus igniarius. Destruction of Oak- 

 wood under the comVjined agency of 

 both fungi. The wood is yellowish and 

 perforated ; the medullary rays are 

 snowy-white, from the accumulation of 

 unchanged starch, (v. Tubeuf phot.) 



where this fungus does great harm. They are also found, how- 

 ever, on bark of living stems of spruce and fir. The destruction 

 takes the form of a red-rot, the wood attacked becoming red- 

 brown, cracked, and soft. The mycelium is found in stems and 

 roots of trees ; in cracks in the wood and below the bark, and 

 on the surface of timber in buildings, it forms fan-shaped strands 

 of a permanent white colour. The mycelial strands of the 

 "dry-rot fungus" (Mcrulius /<///, ,/<inx) differ from it in being 



1 Very common in Britain on dead wood, less so on living trees. (Edit.) 



