Summary:
Features include 1) resupinate growth on wood, 2) a whitish to creamy yellow fruitbody that is smooth at first, developing conic spines but practically always with smooth hymenium remaining in between, the tips of the spines brush-like under 50x lens, the margin indistinct at first, becoming more distinct, 3) spores that are elliptic, smooth, inamyloid, and colorless, with one to a few oil droplets, 4) cystidial capitate hyphae that are frequent, the head normally encrusted, and 5) a monomitic hyphal system, the hyphae with clamp connections, when young more or less cyanophilic, when old having lots of crystals in the hyphal texture and attached to hyphae in the spines.

Microscopic:
SPORES 5-6 x 3.5-4.5 microns, elliptic, smooth, thin-walled, with one (or a few) oil droplets, "in herbarium specimens often as irregular oily bodies, eventually disappearing"; BASIDIA 4-spored, at first subclavate, then subcylindric with median suburniform constriction, mostly 18-20 x 4-5 microns (in young hymenia often longer, up to 25 microns), with basal clamp connection; CYSTIDIA none, but "cystidial capitate hyphae frequent in the hymenium and in the aculeal apices", the head normally encrusted but the encrustation often disappearing in slides, "differentiation of the sterile hyphal ends varying from simple obtuse hyphal ends to capitate, often swollen organs" that could be regarded as cystidioles or even cystidia; HYPHAE monomitic, 2-3 microns wide, distinct, colorless, "with thin or slightly thickened walls", with clamp connections, "rather straight and sparsely branched" in the center of the aculei, "irregularly intertwined and densely branched in the subiculum, in the mature subhymenium thinner and denser, more or less perpendicular to the hymenial surface"; young hyphae more or less cyanophilic; "in old specimens lots of crystals in the hyphal texture and attached to the aculeal hyphae", (Eriksson), SPORES 5-6.5 x 4-5 microns, oval, smooth, inamyloid, colorless, with droplets; BASIDIA 4-spored, 20-25 x 4-5 microns, narrowly clavate, with basal clamp connection; CYSTIDIA: cystidia-like capitate hyphal ends, 30-45 x 2.5-4.5 microns, smooth, the distal capitate ends up to 7.5 microns across; HYPHAE monomitic; projecting hyphae of the spines 2.5-4 microns wide, thin-walled, incrusted with crystals; hyphae of the subhymenium branched, thin-walled, with clamp connections, (Breitenbach)

Notes:
Hyphodontia granulosa has been found in BC, ON, PQ, AK, AZ, CO, and MN, (Ginns), BC, TN, Austria, Germany, Norway, Poland, Sweden, and China, (Langer), Switzerland (Breitenbach), and all parts of Scandinavia, from Denmark to north Lappland, (Eriksson).