Summary:
Features include 1) resupinate growth on wood of conifers or less often hardwoods, 2) pliant, tough-leathery fruitbodies that are whitish to buff, the surface smooth to tuberculate, the margin abrupt or thinning out, 3) spores that are 4-5.5(8) x (2)2.5-3 microns, elliptic to cylindric, flattened on the adaxial side, smooth, colorless, and amyloid or not (amyloid reaction distributed evenly or limited to a small part of the adaxial surface), 4) cystidia that are cylindric, often with refractive contents, sulfo-positive or sulfo-negative, embedded or projecting, 5) a dimitic hyphal system, the generative hyphae with clamp connections, the skeletal hyphae dextrinoid.

Microscopic:
SPORES 4-5.5(8) x (2)2.5-3 microns, elliptic to cylindric, flattened on adaxial side, smooth, "amyloid or not, amyloid reaction distributed evenly or limited to a small part of the adaxial surface", colorless, acyanophilic, thin-walled, BASIDIA 4-spored, 20-35 x 3-4 microns, clavate, colorless, thin-walled, with clamp connection at base, CYSTIDIA scattered to numerous throughout subiculum and hymenium, 40-60(120) x 2-5 microns, embedded or slightly projecting, best observed in phloxine, cylindric, with rounded or tapered apex, colorless, thin-walled, clamped at base, flexuous [wavy], often with refractive, globular contents, positive or negative in sulfobenzaldehyde; HYPHAE dimitic; SUBICULUM consisting of fiber [skeletal] hyphae, generative hyphae and cystidia in a dense, tightly interwoven tissue, subicular hyphae 2-8 microns wide, "thin-walled, nodose septate, moderately to frequently branched, hyphae next to substrate arranged horizontally, otherwise vertical"; fiber [skeletal] hyphae 1-3.5 microns wide, colorless, "thick-walled, aseptate, sparingly branched, dextrinoid", abundant throughout fruitbody, best observed in Melzer''s reagent, (Nakasone), DENDROHYPHIDIA densely interwoven, strongly dextrinoid in Melzer''s reagent; gloeocystidia embedded or projecting, (Martin), SPORES 3.5-5.5(7) x (2)2.3-3(3.2) microns; BASIDIA (15)25-40 x (2)3-5 microns; GLOEOCYSTIDIA abundant, 30-120 x 3-6.5 microns, cylindric to fusoid; SKELETAL HYPHAE 1.5-3.5 microns, (Julich)

Notes:
Scytinostroma galactinum has been found in BC, WA, OR, ID, AB, MB, NB, NF, NS, ON, PE, PQ, SK, AK, AL, AR, AZ, CA, CO, CT, DE, FL, GA, IL, IN, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, NH, NM, NY, OK, SC, SD, TN, TX, VA, VT, WI, WV, and WY, (Ginns(5) in 1993). Nakasone(7) commented that descriptions by previous researchers (previous to 1988) are S. galactinum and S. protrusum combined or of S. protrusum).

Synonyms and Alternate Names:
Phlebia concentrica (Cooke & Ellis) Kropp & Nakasone
Radulum concentricum Cooke & Ellis