POLYPOKUS. 



439 



Seynes,^ three other kinds of spores are produced in addition 

 to basidiospores. 



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 riclier 

 in carbo-hydrates, and the walls of 

 the wood-fibres 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, brittle, and powdery. 



Polyporus borealis (Wahlenb.) Fr.^ (Britain and U.S. 

 America). Sporophores annual, white, and fleshy ; the upper 



Fig. 26S. — Polyporus sutphureus. 

 Hymenial layer, with basidia and 

 spores. (After R. Hartig.) 



Fig. 2(39. — Potypoi-uJ; siUphureus. The white mycelium forms concentric zones 

 and radial lines on the cross-section of Oak. (After R. Hartig.) 



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

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



^De Seynes, Amud. dn Sci. imt.. Set: V., Vol. i., 

 ^ R. Hartig, Zersetzungnerscheinungen, PI. X. 



1864. 



