Summary:
Features include 1) resupinate growth on bark of conifers, 2) corticioid, effused, readily confluent fruitbodies that are white, aging cream to pale yellowish, with a powdery texture, cracked with drying, the margins adnate, and finally abrupt, 3) spores that are nearly round, finely spiny, amyloid, and relatively small, 4) a hymenium consisting of obscured basidial elements, simple paraphysoids, deep-seated pseudocystidia that darken in sulphobenzaldehyde, and acanthophyses, and 5) context that is monomitic with tips of hyphal branches capped by prongs.

Microscopic:
SPORES 5-7 x 5-6 microns, nearly round, slightly flattened adaxially, echinulate [finely spiny] in Melzer''s reagent, amyloid, firm-walled, apiculate; catahymenium consisting of obscured basidial elements, simple paraphysoids, deep-seated pseudocystidia, and acanthophyses; BASIDIA (2)4-spored, 30-45 x 5-7 microns, flexuous-cylindric to subclavate, basidioles "subclavate to clavate, maturing by an external prolongation"; PARAPHYSOIDS scattered, 3-4 microns wide, cylindric, simple to singly branched; PSEUDOCYSTIDIA (macrocystidia) 55-80 x 5-6(8) microns, flexuous-cylindric, rarely with an apical gemma, contents of pseudocystidia yellowish in KOH, darkening in sulphobenzaldehyde; ACANTHOPHYSES cylindric, mostly 3-4 microns wide, basal part thin-walled and naked, aculeate-pronged part semi-solid, borne at apex, these terminal pronged parts seen to advantage in Melzer''s reagent, "separable and then appearing as free-floating fragments" measuring 7-15 x 4.5-6 microns; CONTEXT monomitic, composed of hyphae that are 1.5-3 microns wide, irregular, branched, clamped, walls thin to partially thickened, "tips of hyphal branches capped by a semisolid, aculeate-pronged apex", (Lemke)

Notes:
Acanthophysium weirii has been recorded from BC, OR, ID, AK, AZ, MI, and MT, (Ginns(5)).

Synonyms and Alternate Names:
Cantharellus fasciculatus Schwein.
Cyphella fasciculata (Schwein.) Berk. & M.A. Curtis