440 



BASIDIOMYCETES. 



many generally grow near each other. The pores have a torn 

 margin and cystids are frequent between the basidia. 



The sporophores are common in spruce plantations, and are 

 accompanied by a very characteristic wood-destruction. The 

 wood, in the earlier stages, becomes brownish-yellow and inter- 

 sected by radial and vertical canals filled with a white mycelium 

 (Fig. 270). Gradually, however, it breaks up into small cube- 



FlG. 270. — Poti/poTus horeaUs. Destruction of FlQ. 271. — Poli/porus horeatis. Later stage 



Spruce-wood. The white mycelium is present, of destruction.- The Spruce-wood is broken 



dividiDg the decayed wood into cubical pieces. up into cubical pieces, and the mycelium has 



(v. Tubeuf phot.) disappeared, (v. Tubeuf phot.) 



like pieces, particularly evident when the wood is broken (Fig. 

 271). The cell- walls are dissolved from the cell-cavity out- 

 wards, the lignified wall being fii-st converted into cellulose and 

 disappearing, finally the middle lamella. 



Polyporus dryadeus Fr.^ {P. psevdoigniarivs Bull.) (Britain 

 and U.S. America). Sporophores, annual, large, shaped like 

 tubers or hoofs, and generally situated towards the base of the 



'R. Hartig, Zersetzunyserscheinungen, PI. XVII. A common British species. 



