Summary:
Features include 1) resupinate growth on a variety of hardwoods and shrubs, 2) fruitbodies that are cream to pale ocher, and smooth to somewhat uneven, the margin distinctly bounded, in part thinning out, 3) spores that are round, smooth, amyloid, and colorless, with a distinct apiculus, 4) 2-4-spored basidia, 5) gloeocystidia that are scarce or absent, and 6) a dimitic hyphal system, the hyphae without clamp connections, the skeletal hyphae dextrinoid. Adolf and Oluna Ceska report that patches on Robinia (locust) have a strong naphthalene (mothball) odor.

Microscopic:
SPORES 5-5.5(6) microns in diameter, round, smooth, amyloid, colorless, with distinct apiculus; BASIDIA 2-4-spored, 25-40 x 5-6 microns, cylindric-clavate, without basal clamp connection; CYSTIDIA not seen; HYPHAE dimitic; GENERATIVE HYPHAE 1.5-2.5 microns wide, "thin-walled, sparsely septate", without clamp connections; SKELETAL HYPHAE 1.5-2.5 microns wide, "thick-walled, branched, dextrinoid, some solid", ends generally straight; subhymenium and subiculum stratified by parallel skeletal hyphae (stratification also visible with a hand lens), (Breitenbach), SPORES 4.5-6 x 4.5-5.5 microns, round to broadly elliptic; BASIDIA 30-55(65) x (4)4.5-6(7) microns; GLOEOCYSTIDIA scarce or absent, 30-70 x 3-5 microns; GENERATIVE HYPHAE 1.2-3 microns wide; SKELETAL HYPHAE 1.5-2.5 microns wide, ultimate part "simple or rarely once branched, branches then very long, not dendroid, almost forming a layer, parallel to and along the hymenium", (Julich)

Notes:
Scytinostroma portentosum has been found in BC, ID, ON, AK, AL, AZ, CA, FL, IN, KY, LA, ME, MO, NY, OH, PA, TX, VA, and VT, (Ginns). It has also been found in Europe including Switzerland, and in Asia, (Breitenbach).