POLYPORUS. 



439 



Seyiies,^ three other 

 to l)usidiospores. 



Willow, poplar, oak, sweet chest- 

 nut, alder, ash, hazel, pear, cherry, 

 robinia, larch, silver fir, etc., are 

 common hosts of this parasite. 



Wood infested by the mycelium 

 darkens in colour, exhibiting a red- 

 rot. Vessels and all clefts or spaces 

 become filled with white felted 

 masses of mycelium. The wood, in 

 course of destruction, becomes richer 

 in carbo-hydrates, and the walls of 

 the wood-tibres shrink so that fis- 

 sures with an upward right to left 

 direction are formed, but do not reach 

 the middle lamellae. Finally the 

 wood becomes dry, l)rittle, and powdery. 



Polyporus borealis (Wahlenb.) Fi 

 America). Sporophores annual, white. 



kinds of spores aie produced in addition 



'i ' ^ t. 



Fio. 2<i8. — Poli/porut gulphurevJi. 

 Hymeiiial layer, with basidia and 

 spores. (After R. Hartig.) 



" (r»ritain 

 and fleshy ; 



and U.S. 

 the upper 



Fio. 2t)!>. Pohn'orv^ xalplmrcus. The white niyceliuni forms concentric zones 



and radial lines on the cross-section of Oak. (.\fter R. Harti(j.) 



surface is shaggy when fresh, and no internal zones are exhibited. 

 The shape is somewhat cushion or bracket-like, but very variable ; 



1 De Seynes, Annul, de Sci. nat, Ser. V., Vol. i., 1SC4. 

 -R. Hartig, Zersetzungierscheinungen, PI. X. 



