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Species Information
Summary: {See also Stereum Table.} Features include 1) resupinate growth on hardwood, or less often with cap-like marginal zones, which may form dense shingled clusters, 2) when present, a cap that is leathery, narrow, wavy or lobed, at first finely tomentose and grayish, soon becoming bald and dark brown, finally black in narrow and sharp zones, 3) a spore-bearing surface that is smooth to uneven or tuberculate, pale ochraceous to buff, bleeding when cut or touched in fresh state, the fluid first reddish, but soon blackish brown, 4) a margin that is white to pale ochraceous and rounded, 5) a distinctly layered appearance in section, each yearly zone defined by a thin dark line, 6) spores that are elliptic, smooth, amyloid, and colorless, 7) pseudoacanthohyphidia, thick-walled cystidia arising from thick-walled skeletal or skeletoid hyphae, and presumably sharp-tipped hyphidia, and 8) hyphae of 2 types a) thin-walled to thick-walled, with frequent branching, septa without clamp connections, and b) thick-walled, sparsely branched, without septa. |Stereum ostrea, Stereum rugosum, and Stereum sanguinolentum are members of the subgenus Aculeatostereum which have pseudoacanthohyphidia: thin-walled hymenial elements that bear a few (2-5, rarely up to 10) apical projections (also known as pseudoacanthophyses, aculeate-tipped basidioles, acanthocystidia, and acanthohyphidia, by different authors, the last term also used for acanthophyses - with projections throughout their length - that occur in subgenus Acanthostereum not found in North America), (Chamuris(3)).
Stereum rugosum has been found in BC, ID, NB, NF, NS, ON, PE, PQ, AK, MI, MN, NC, NH, NY, PA, and TN, (Ginns). It is common in Scandinavia (Eriksson), and occurs also in Switzerland and Asia, (Breitenbach).
Fruiting body: resupinate, more rarely in old specimens with slightly projecting, brown, cap-like marginal zones, forming patches 0.05-0.2(0.3)cm thick and several centimeters to decimeters across, when fresh leathery and tough (when dry hard and crustose, brittle); surface "smooth to uneven or tuberculate, dull, whitish, ocherish to orange-gray, also gray-pink or if wet grayish, when fresh or moist turning red when injured"; margin distinctly bounded; in cross-section a distinct layering is recognizable in fruitbodies several years old (according to the literature up to 20 layers), (Breitenbach), resupinate to effused-reflexed [bent outward to form shelf-like cap], coriaceous [leathery] to very hard, "first as rounded and orbicular patches, usually with a loosening margin", then with a narrow reflexed cap forming dense imbricate clusters; cap when present narrow, "undulate to lobate, often fused laterally", rarely more than 1cm wide, mostly narrow, at first finely depressed tomentose and grayish, soon becoming bald and dark brown, "finally black in narrow and sharp zones and with a distinct cortex in section"; "margin white to pale ochraceous and rounded"; spore-bearing area "smooth, tuberculate to undulating, pale ochraceous to buff", when old "pale yellowish brown, often with black spots in old specimens", "bleeding when cut or touched in fresh state, fluid first reddish, but soon blackish brown"; in section, the fruitbody distinctly layered, "each zone clearly defined by a thin dark line", totally up to 0.2cm thick, ochraceous in younger parts, darker and often grayish to dirty brown in old parts as the content of the pseudocystidia becomes oxidized with age to a dark-colored substance, (Eriksson), spore deposit white (Buczacki)
Microscopic: SPORES 6.5-9 x 3.5-4.5 microns, elliptic, sometimes flattened on one side, smooth, amyloid, colorless; BASIDIA 4-spored, 25-40 x 5-7 microns, narrowly clavate, without basal clamp connection; PSEUDOACANTHOHYPHIDIA with pointed outgrowths, 25-35 x 3-4 microns; CYSTIDIA none, but ends of conducting hyphae emerging from skeletal hyphae 5-6 microns wide, up to over 250 microns long, cylindric to acuminate, thick-walled, some with brown-reddish contents; HYPHAE dimitic, generative hyphae 1.5-3.5 microns wide, thin-walled to thick-walled, septa without clamp connections, skeletal hyphae up to 8 microns wide, thick-walled without septa, (Breitenbach), SPORES 7-12 x 3-4.5 microns, narrowly elliptic to cylindric, slightly bent, smooth, amyloid, thin-walled; BASIDIA 4-spored, 30-50(100) microns, elongated clavate; CYSTIDIA of 2 types: 1) pseudoacanthohyphidia easily observed, 30-35 x 3-4 microns, projecting slightly beyond the basidia, 2) pseudocystidia 5-12 microns wide, usually more than 100 microns long, "thick-walled, except for the apical part, slightly projecting, smooth, more or less constricted", colorless to yellowish, with oily content; HYPHAE monomitic with simple-septate hyphae of 2 types, "hymenial hyphae thin-walled, 3-4 microns wide, branching frequent, tramal hyphae thick-walled, horizontal, 3-6 microns wide, hyphae in the tomentum are of an intermediate type, sparingly branched, hyaline to yellowish and in cortex pale brown and fairly thick-walled", (Eriksson), SPORES 7-12 x 3-6 microns, PSEUDOACANTHOHYPHIDIA present and [on the basis of subgenus definition] acuminate-tipped (sharp-tipped) HYPHIDIA, (Chamuris)
Habitat / Range
on dead, standing or fallen wood of hardwoods, with and without bark; throughout the year, (Breitenbach), on hardwood of many kinds, especially on standing dead trunks where it can cover large areas, (Eriksson), on various hardwoods, also reported from Abies (fir), Picea (spruce) and Pseudotsuga (Douglas-fir), (Ginns)
Similar Species
Stereum sanguinolentum also has pseudoacanthohyphidia [and turns red with bruising], but grows on conifers, and lacks the multiple hymenial layers, (Chamuris(3)). |Stereum ostrea also has pseudoacanthohyphidia [and turns red with bruising], but 1) has a fruitbody that is leathery, capped, substipitate or effuso-reflexed, whereas S. rugosum has a hard fruitbody that is resupinate or with slightly reflexed margins, 2) is annual or occasionally biennial, (S. rugosum perennial with multiple hymenial layers), 3) has smaller spores (4-7 x 2-3 microns), and 4) is common in North America south of 42 degrees latitude, whereas S. rugosum is rare in North America, (Chamuris(3)). |For other Stereum species that turn red with bruising see SIMILAR under S. sanguinolentum. |See also SIMILAR section of Stereum gausapatum.
