448 



BASIDIOMYCETES. 



pinuurii Bresadola or P. fulvus Scop, of II. Hartig). Sporophores 

 on silver fir, less commonly on spruce. Their form varies much, 

 according as they occur on a branch or on the stem. In the 

 former case, the sporophore forms a swelling below and on each 

 side of the more or less horizontal branch. On the stem they 

 are more or less bracket-like. The sporophores are reddish 



brown with a smooth upper surface on 

 which zones are only faintly indicated 

 or altogether absent. Internally they 

 are of a brownish or tawny colour, and 

 exhibit concentric strata, which, do not 

 extend into the pore-layer; they are thus 

 distinguished from sporophores of P. 

 ii/nhcrius and others. The sporophores 

 are very frequent on cankered stems of 

 fir where the canker-spots afford easy 

 entrance for the spores. 



The wood-destruction consists in a 

 white -rot. The wood becomes yellowish- 

 white with clear spots and fine dark 

 lines, especially where in contact with 

 healthy parts. The mycelium is yellow- 

 ish, and consists of thick hyphae with 

 lateral, branches forming tangled masses 

 which frequently fill up the cavity of 

 the bordered pits. This mycelium gives 

 off very fine branches which bore through 

 the cell-walls and dissolve them in such 

 a way that the middle lamellae disappear 

 first and leave the remainder of the wall- 

 thickening for a time isolated before it 



too is used up. In this way large holes are formed in the 

 elements of the wood. 



Polyporus sistotremoides (Alb. et Schw.) (P. Schweinitzii 

 Fr. or P. mollis Fr. of It. Hartig) 1 (Britain). Sporophores almost 

 circular with a short thick central stalk ; while young they 

 are light brown and spongy, but when older become dark brown 

 and corky. The upper surface is downy ; the hymenial layer 

 extends far down the stalk, when young it is yellowish green, 



1 R. Hcirtig, Zersetzungserscheinungen, PI. IX. 



V 



PIG. 279. Polyporus Hartigii. 

 Destruction of wood of Silver Fir. 

 The decayed wood is yellow, but 

 shows dark points and black lines, 

 (v. Tubeuf phot.) 



