Summary:
Sistotrema adnatum is a member of the Sistotrema brinkmannii group, described as follows, "Fruitbodies effuse, smooth or grandinioid; hyphae with clamps, walls hyaline; gloeocystidia absent; basidia urniform, normally with 6-8 sterigmata; spores less than 9 microns long, ellipsoid, subcylindrical, suballantoid, or subglobose, uninucleate (except for S. binucleosporum)", (Hallenberg, Latin name underlined). It is "distinguished by the adnate fruitbody with a continuous hymenium, the wide subicular hyphae with large ampullate clamps and the compact subhymenium", (Hallenberg).

Microscopic:
SPORES 6-8 x 2.8-3.3 microns, elliptic, adaxial side straight, smooth, thin-walled; BASIDIA 6-spored, 19-27 x 4.5-5.5 microns, urniform, with basal clamp connection; HYPHAE monomitic, with clamp connections that frequently are ampullate (up to 15 microns wide); SUBHYMENIAL HYPHAE 3.5-6 microns wide, richly branched, thin-walled, contents somewhat oily; SUBICULAR HYPHAE 4-7.5 microns wide, interwoven (but more or less parallel to the substrate), straight, colorless, slightly thick-walled, sparsely septate, (Hallenberg)

Notes:
The holotype is from BC (Hallenberg).