Summary:
Features include 1) resupinate growth on wood, 2) a soft, fibrous, cottony, often bumpy fruitbody that is granular and honey-yellow to brownish in the center and toward the margin increasingly filamentous and bright yellow, ending in whitish rhizomorphs, 3) a fruitbody that turns wine-red in KOH, 4) spores that are nearly round to elliptic, with dense short spines, inamyloid, and colorless, 5) pleural basidia, and 6) a monomitic hyphal system, the hyphae with clamp connections, the subhymenial hyphae richly branched and sinuous, the subicular hyphae straight and often encrusted with crystals.

Microscopic:
SPORES 4-5.5 x 3.5 microns (excluding spines), elliptic, short-spined, inamyloid, colorless; BASIDIA 4-spored, 13-22 x 5-6.5 microns, clavate, with basal clamp connection; CYSTIDIA not seen; HYPHAE monomitic, 3-5 microns wide, yellowish, in part encrusted, with clamp connections, (Breitenbach), SPORES (4.5)5-5.5(7) x 4-4.5 microns, subglobose to elliptic, densely verruculose, inamyloid; BASIDIA subspherical to subclavate, sinuous, pleural, mainly 15-20 x 5-6 microns, 4-spored, with basal clamp connection; HYPHAE monomitic, with clamp connections, thin-walled; subicular hyphae and rhizomorph hyphae 2-5 microns wide, straight, "often provided with crystals and now and then with slightly ampulliform septa, slightly agglutinated", subhymenial hyphae 2-3 microns wide, sinuous, richly branched, hyphae turning vinaceous red in KOH, (Hjortstam)

Notes:
Xenasmatella vaga has been found in BC, WA, ID, AB, MB, NB, NS, ON, PQ, AK, AL, AZ, CA, CO, IL, IN, MA, MD, MI, MN, MO, MT, NC, NH, NJ, NM, NY, OH, PA, TN, UT, VT, and WI, (Ginns). It is the most common species of the genus and widespread in Scandinavia (Hjortstam). Distribution also includes Switzerland and Asia (Breitenbach).