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Species Information
Summary: Boreostereum radiatum is "readily recognized by its bright, ferruginous hymenium with shallow broad ridges radiating from the center to the margin, and by the black upper side of the pileus when reflexed", (Burt). Features include 1) resupinate growth on wood, with the margin free all round and sometimes bent outward on the upper side to form a shelf-like cap, 2) a leathery fruitbody, with the spore-bearing surface rusty brown, uneven, with radiating thick ridges, 3) a cap when present that becomes black, velvety, crisped, and somewhat lobed, 4) spores that are slightly curved, smooth, and inamyloid, 5) cystidia that are thin-walled and lightly encrusted, 6) a dimitic hyphal system, the septa without clamp connections, and 7) sections staining yellow-green in KOH.
Boreostereum radiatum has been found in BC, WA, ID, AB, MB, ON, PQ, AZ, IA, MA, ME, MI, MN, MT, NH, NY, PA, TN, VA, VT, and WI, (Ginns(5)). Collections were examined from ON, MA, MI, MT, NY, PA, VT, and Russia, (Burt).
Fruiting body: "resupinate, with the margin free all around, sometimes reflexed on the upper side", coriaceous [leathery], 0.1cm thick, 2cm in diameter up to 10cm x 3cm, the reflexed part 0.2-0.8cm broad, becoming black above, velvety, crisped, and somewhat lobed; hymenial surface Sudan-brown (Ridgway color), rarely black when turned upward and exposed to direct sunlight and weather; hymenium "uneven, not polished, marked with thick ridges radiating from the center", (Burt), resupinate to effused-reflexed; rusty brown, often turning blackish; with radially arranged ridges, (Martin), effuse to reflexed, leathery, spore bearing surface brown to ferruginous, smooth to wrinkled, cap or reverse of spore-bearing surface black, (Ginns(23))
Microscopic: SPORES 7.5-10 x 3-3.5 microns, inamyloid; CYSTIDIA 2-4 microns wide, thin-walled, lightly encrusted; HYPHAE dimitic, generative hyphae simple-septate, (Martin), SPORES from spore collections 9-10 x 3.5-4 microns, slightly curved, smooth, white; hyphae 3.5-4 microns wide, densely and longitudinally arranged, colored, but color dissolved by dilute KOH; no CYSTIDIA, (Burt), microscopic sections staining yellow-green in KOH, HYPHAE dimitic: generative hyphae simple-septate, and skeletal hyphae yellow, (Ginns(23))
Habitat / Range
charred wood and logs; logs; boards; associated with a white rot; Larix laricina (Tamarack), Malus sylvestris, Picea engelmannii (Engelmann spruce), Picea glauca (White Spruce), Picea mariana (Black Spruce), Picea rubens (Red spruce), Pinus sp. (pine), Populus tremuloides (Quaking Aspen), Thuja occidentalis (Northern White-cedar), Tsuga canadensis (Eastern Hemlock), (Ginns(5)), underside of hemlock, spruce, and pine boards and logs and charred wood, (Burt)
Similar Species
The general aspect, color, and color changes with KOH are suggestive of some species of Hymenochaete, but no setae are present, (Burt).
