Bjerkandera fumosa

Bjerkandera fumosa is a species of poroid fungus in the family Meruliaceae.
Taxonomy.
It was first described to science as "Boletus fumosus" by Christiaan Hendrik Persoon in 1801. Petter Adolf Karsten transferred the species to the genus "Bjerkandera" in 1879.
Description.
The form of "Bjerkandera fumosa" fruit bodies ranges from effused-reflexed (spread out over the substrate and turned back at the margin to form a cap) or cap-like, but attached directly to the substrate without a stipe. These caps can be solitary or closely overlapping, and are often fused with neighbouring caps. The caps typically measure wide by wide, and a buff-coloured upper surface with a texture ranging from finely hairy (tomentose) to smooth. The pores on the cap underside are circular to angular, numbering 2–5 per millimetre.
"Bjerkandera fumosa" has a monomitic hyphal system, containing only generative hyphae. The basidia are club-shaped, measuring 20–22 μm. Spores have the shape of short cylinders, and measure 5.5–7 by 2.5–3.5 μm. They are smooth, hyaline, and do not react with Melzer's reagent.
Habitat and distribution.
"Bjerkandera fumosa" causes a white rot in various hardwood species. It has a circumboreal distribution in the Northern Hemisphere.