Hohenbuehelia atrocaerulea var. grisea
Cap sessile to substipitate, dorsally to laterally attached, 1.0-2.5 cm broad, at first inverted-cupulate, then shell-shaped or pleurotoid; margin incurved, then decurved, occasionally wavy; surface greyish-black, to dark greyish-brown (bluish-black in one variety) fading to medium-brown; upper surface distinctly hairy at the attachment point, elsewhere patchy-tomentose; context thin, two-layered, upper layer gelatinous, greyish-blackish, lower layer, soft, watery-white; fruiting body capable of reviving after drying; odor and taste slightly farinaceous.
Gills radiating from the attachment point, fairly well-spaced, relatively broad, pale-grey in youth, becoming whitish, then cream-colored in age; lamellulae in up to three series.
Spores 6.0-9.0 x 3.0-4.0 µm, cylindrical-elliptical in face-view, bean-shaped in profile, smooth, thin-walled, inamyloid, white in deposit; metuloid cystidia present.
Scattered to clustered on the undersurface of rotting hardwood branches and logs, occasionally with conifers; frequently found with Bush Lupine, Lupinus arboreus, otherwise uncommon; fruiting from mid to late winter.
Too small to have culinary value.
Resembling an oyster mushroom, but much smaller, Hohenbuehelia atrocaerulea var. grisea is recognized by a greyish-black, sparsely tomentose cap, and gills which become cream-colored in age. A bluish-black variant, appropriately called var. caerulea is also known but appears to be less common. Characteristic of the genus, the cap context of Hohenbuehelia atrocaerulea var. grisea is partially gelatinous, a feature that can be seen by sectioning the cap and examining with a hand-lens. Similar to Hohenbuehelia atrocaerulea var. grisea is Hohenbuehelia mastrucatus, a small greyish species that differs in possessing gelatinous spines near the cap margin and broader spores. Compare also with Resupinatus applicatus and Panellus spp. Resupinatus applicatus forms grey-brown, diminutive shelves on the undersurface of downed hardwoods, but is smaller, seldom larger than 5.0 mm broad, and remains inverted cupulate throughout development. Microscopically it is distinguished by the lack of metuloid type cystidia. Panellus species can be separated by their amyloid spores.