Summary:
Features include 1) resupinate growth on wood and other substrates, 2) a fruitbody that is a thin gray layer, waxy-pruinose when fresh, 3) spores that are smooth, inamyloid, and oval to elliptic, germinating by repetition, 4) 4-spored, roundish basidia with large sterigmata, and 5) a monomitic hyphal system without clamp connections.

Microscopic:
SPORES 7-11.5 x 3.5-6 microns, narrowly oval to elliptic, smooth, inamyloid, spore repetition occurs laterally; BASIDIA 4-spored, 12-16 x 7-10 microns, sterigmata 10-15 microns long; CYSTIDIA none; HYPHAE monomitic, BASAL HYPHAE about 5 microns wide, with somewhat thickened walls, straight, sparsely branched at right angles, no clamp connections, hymenial branches more narrow, thin-walled and richly branched especially in old hymenia, no clamp connections, "finally forming a pseudoparenchymatous structure", (Eriksson), SPORES (6.5)7.5-9.5 x 4-6 microns, "broadly fusiform in one aspect, asymmetrical, oblong-ellipsoid, obliquely attenuate in the other", germinating by repetition; BASIDIA 12-14 x 7.5-9(11) microns, "terminal or lateral on the supporting hyphae, ovate or pyriform", "bearing on the end or on the outer side four stout epibasidia, straight or somewhat curved or divergent, sometimes inflated just above the base", 9-12(14) x 2-3 microns; hyphae (3)5-6(7.5) microns wide, "colorless, without clamps, mostly repent, branching at right angles", (Martin)

Notes:
Ceratobasidium cornigerum has been found in OR, AB, ON, CO, IA, IL, NY, and OH, (Ginns). It has also been found in Europe and the Marshall Islands, (Martin). There are collections from BC deposited at University of British Columbia by R. Bandoni.

Synonyms and Alternate Names:
Corticium cornigerum Bourdot
Pistillaria thaxteri Burt
Pistillina thaxteri (Burt) Corner