Summary:
Features include 1) resupinate growth on conifer wood, 2) cream to buff or bright yellow fruitbodies with hairs, 3) spores measuring 7.5-9.5 x 3.5-5 microns that are elliptic to broadly fusiform or navicular, 4) 4-6-spored basidia that are subcylindric to suburniform, 5) abundant cystidia that are cylindric to subfusiform, smooth, and thin-walled, and 6) wide subicular hyphae with right angle branching, the walls up to 2.5 microns thick, with clamp connections.

Microscopic:
SPORES 7.5-9.5 x 3.5-4.5 microns, elliptic to broadly fusiform, inamyloid, colorless, illustrated as smooth with obvious apiculus; BASIDIA 4-6-spored, 8-10 microns wide, usually with slight median constriction; CYSTIDIA abundant, 50-110 x 6-10 microns, cylindric, thin-walled, non-septate; SUBICULAR HYPHAE 5-8 microns wide, with conspicuous right angle branching, thin-walled, nodose-septate, (Gilbertson), SPORES 7.5-9 x 3.5-4 microns, elliptic to broadly fusiform; CYSTIDIA abundant, cylindric, thin-walled; hyphae with clamp connections, (Martin), SPORES 8-9 x 4-5 microns, navicular to broadly fusiform; BASIDIA (4)6-spored, 17-29 x 8-10 microns, subcylindric to suburniform; CYSTIDIA 55-120 x 8-12.5 microns, cylindric to subfusiform, colorless, smooth, thin-walled to slightly thick-walled; HYPHAE 7-15 microns wide, the basal ones with thickened walls (up to 2.5 microns), according to key lead with clamp connections, "at least sub-basidial and at the basal hyphae", (Julich)

Notes:
Botryobasidium ansosum has been found in BC, WA, AZ, CA, and NM, (Ginns).

Synonyms and Alternate Names:
Polyporus aneirinus Sommerf.: Fr.
Poria aneirina (Sommerf.: Fr.) Cooke