AUTOBASIDIOMYCETES 



463 



Polyporus borealis (Wahl.) Fr. is a characteristic and destructive 

 disease of the spruce in Europe, and it occurs on a variety of conifers 

 in America. 1 The bracketed sporophores are clustered, as shown 

 in Fig. 228. They are fleshy for some time, but finally tough and 

 dry. The s.pores are minute, measuring 4-5 x 3 p. The mycelium 

 develops abundantly in the wood with typical markings (Fig. 229). 



Fig. 229. Polyporus borealis: Longitudinal Section of Log, 

 showing Mycelium. (Photograph by Geo. F. Atkinson) 



Polyporus carneus Nees causes a red rot, or peckiness, in the 

 common red cedar (Juniperus virginiana) and in the southern red 

 cedar (Juniperus barbadensis), as well as in other conifers. 2 



Polyporus Juniperinus von Schrenk is apparently the cause of 

 the white rot of the red cedar. 2 



Polyporus Schweinitzii Fr. is abundant in Europe on the Scotch 

 pine, Weymouth pine, and the larch. 3 This species is yellowish 



1 Atkinson, Geo. F. Cornell Agl. Exp. Sta. Built. 193 : 202-208. 1901. 



2 Schrenk, H. von. Div. Veg. Phys. and Path., U. S. Dept. Agl. Built. 21 : 1-22. 

 ph. i-y. 1900. 



s Schrenk, H. von. Div. Veg. Phys. and Path., U. S. Dept. Agl. Built. 25 : 18-24. 



