Summary:
Features include 1) resupinate growth on wood, 2) a fruitbody that is thin, flat, cottony, and whitish, 3) spores that are elliptic to slightly navicular, 4) 6-spored basidia, and 5) a monomitic hyphal system, all septa with clamp connections, the basal hyphae wide and thick-walled.

Microscopic:
SPORES 6-9 x 3-3.5 microns, elliptic to slightly navicular [boat-shaped], smooth, inamyloid, colorless, cyanophilic; BASIDIA 6-spored, 15-25 x 6-10 microns, cylindric, with basal clamp connection; CYSTIDIA not seen; HYPHAE monomitic 5-10(12) microns wide, thin-walled to thick-walled, all septa with clamp connections, (Breitenbach), SPORES 6-7.5 x 2.5-3 microns, navicular with distinct apiculus, smooth; BASIDIA mostly 6-spored, 20-25(30) x 7-9 microns, "at first rounded or ellipsoid, then longer and more subcylindrical, more or less constricted"; HYPHAE monomitic: hyphae loosely interwoven, clamped, BASAL HYPHAE 7-10 microns wide, thick-walled, colorless, richly branched, (Eriksson)

Notes:
Botryobasidium subcoronatum has been found in BC, WA, OR, ID, MB, NS, NT, ON, PQ, AZ, CA, CO, CT, LA, MA, MD, MI, MN, MO, MT, NC, NH, NJ, NM, NY, PA, RI, TN, VT, and WI, (Ginns), Europe including Switzerland, Asia, (Breitenbach), and Denmark, Norway, Sweden, and Finland, (Eriksson).

Synonyms and Alternate Names:
Polyporus lapponicus Romell