AGARICUS. 



457 



rhizomorphs distribute the fungus in the earth and other dead 

 substrata, as well as bore into the bark of healthy Conifers. 



This parasite attacks not only the indigenous Conifers (spruce, 

 silver fir, pine, larch, and juniper),^ but also the introduced 

 forms — Weymouth pine, Douglas fir, Pinus rigida, Abies Fichta, 

 Picea sitchensis, various Cupressineae, etc. It also seems to attack 

 broad-leafed trees, at least as a wound parasite.^ 



In regard to the interesting structure of the rhizomorphs, 

 and the characteristic mode of wood-destruction caused by 



Fig. 286. — Agaricus meUeus. Sporophore 

 developed from a rbizomorpli-strand ; the 

 other branch bears arrested sporophores. 

 (After R. Hartig.) 



Fig. 287. — Agancus meUeus. Section 

 through a lamella, d. The hyphae forming 

 the substance of the lamella are much 

 branched, and send twigs outwards which 

 end in club-shaped basidia, a ; on many of 

 these are developed sterigmata with apices 

 swollen into spores, b ; c, isolated thread- 

 like arrested basidia projecting above the 

 hymenial layer. (After R. Hartig.) 



this fungus, I give directly the account by Hartig in his 

 " Lehrbuch." ^ " The pathological symptoms can only be ex- 

 plained in the light of the peculiar organization of the- mycelial 

 growth that lives in the cortical tissues. The apex of the 

 rhizomorphs consists of delicate pseudoparenchyma, which, 

 elongating by the division and growth of the cells, produces 

 delicate hyphae on the inside at a certain distance from the 



^ I found it on juniper in the pine-forests near Eberswalde. (Auth. ) 



2 The mycelium does not seem capable of penetrating uninjured broad-leaved 



trees, but B. Hartig {FornU.-naturwiss. Zeitschrift, 1894, p. 428) mentions attack 



and death of cut roots of healthy oaks. 

 ^R. Hartig, Lehrbuch d. Baumkrankheiten, 1889. The translation given 



here is from Prof. Sonierville's English edition of Hartig's text-book, p. 



210. (Edit.) 



