Summary:
{See also Stereum Table.} Features include 1) growth restricted to oak, 2) tough fruitbodies that are resupinate, or bent outwards to form shelf-like caps extending up to 2cm from the wood, often fused in rows, 3) a cap when present that is tomentose or velvety in narrow zones or bald, gray to pale brown, becoming rusty brown, the margin sharp and paler, 4) a spore-bearing surface that is smooth to tuberculate, often folded radially, gray-brown, red-brown, or ocher-brown, bleeding when cut or touched, with reddish fluid (and later discoloring brown), 5) flesh separated from tomentum in cross-section by a dark brown line, 6) spores that are elliptic-cylindric, smooth, weakly amyloid, and colorless, 7) 2-4-spored basidia, 8) conducting hyphae and pseudocystidia each with brownish contents that are usually found, along with sharp-tipped hyphidia, 9) hyphae of two types, both having septa without clamp connections: a) thin-walled to thick-walled hymenial hyphae with transitions to pseudocystidia, b) hyphae of cortex and tomentum thick-walled, not or sparsely branched, in cortex strongly pigmented and glued together by a resinous substance. |Stereum complicatum, Stereum gausapatum, Stereum hirsutum, and Stereum ochraceoflavum are members of the subgenus Stereum, having sharp tipped hyphidia but lacking the pseudoacanthohyphidia found in subgenus Aculeatostereum. |Stereum gausapatum is sometimes included in the Stereum hirsutum complex, e.g. Welden 1971 referred to in Chamuris(4), but excluded by Chamuris(4) on the basis that is can be distinguished reliably (see SIMILAR).

Microscopic:
SPORES 6.5-9 x 3-4 microns, elliptic-cylindric, smooth, iodine reaction very weakly positive, colorless; BASIDIA 2-4-spored, 40-50 x 6-8 microns, narrowly clavate, without basal clamp connection; CYSTIDIA: ends of conducting hyphae very numerous, thin-walled, up to 6 microns wide, with brown-reddish contents; HYPHAE dimitic, generative hyphae 1.5-5 microns wide, thin-walled to thick-walled, septa without clamp connections, skeletal hyphae 3-5 microns wide, thick-walled, (Breitenbach), SPORES 6-9(10) x 3.5-4.5 microns, elliptic to narrowly elliptic, smooth, amyloid, thin-walled; BASIDIA 4-spored, 30-60 x 4-6(8) microns, elongated clavate; CYSTIDIA of 2 types: 1) pseudocystidia, apically thin-walled but otherwise thick-walled, colorless to yellowish and with a grainy to oily content, 5-10 microns wide, often more than 150 microns long, 2) acutocystidia 20-30 x 2-4 microns, projecting slightly and easily observed in thin sections; HYPHAE monomitic, "with two kinds of simple-septate hyphae, hymenial hyphae thin to thick-walled and with transitions to pseudocystidia. Hyphae of cortex and tomentum thick-walled, not or sparsely branched, in cortex strongly pigmented and glued together by a resinous substance", (Eriksson)

Notes:
Stereum gausapatum has been found in BC, WA, OR, MB, ON, PE, AK, AL, AR, AZ, CA, CT, DC, DE, FL, GA, IA, IL, KS, LA, MA, MD, MO, MS, NC, ND, NJ, NY, OH, OK, PA, TN, TX, VA, and WV, (Ginns). It is widespread following oak in the whole of Europe (Eriksson). Distribution is Europe including Switzerland, North America, Asia, Australia, (Breitenbach). Distribution includes Guatemala, Mexico, Italy, Sweden, United Kingdom, and China, (Chamuris(4)).