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Species Information
Summary: Inonotus obliquus forms large black stemless cracked cankers on birch. Fruitbodies on the other hand are quickly deteriorated by insects and weathering and are hard to find even where infected trees are numerous. The pore surface is whitish becoming dark reddish brown. Microscopically, there are scattered setae that do not project prominently. Claims are made for its use as a medicinal agent.
Inonotus obliquus has been found in BC, ID, AB, MB, NB, NS, NWT, ON, PE, PQ, SK, AR, GA, MA, ME, MT, NH, NY, PA, VT, and WV, and it is circumglobal in boreal forest ecosystems with birches, (Gilbertson). It has also been found in YT (Ginns). It also occurs in Europe and Asia, (Breitenbach).
Cap: "developing beneath the bark or outer layers of wood on dead standing or fallen trees, eventually rupturing the bark", widely spread out, "hard and brittle when dry, becoming easily separable, margin fertile", clinker-like ''sterile conks'' developing on living trees, (Gilbertson), sterile core 25-40cm wide, black; very hard, deeply cracked, fertile part up to 0.5cm thick, crust-like, thin, (Lincoff), sterile conk 25-40cm wide; "black; deeply cracked, very hard and brittle when dry", fertile part 0.5cm thick, crust-like, dark brown, (Phillips), "imperfect form irregularly tuberous", 10cm to 20cm high and wide, projecting 5-10cm from the trunk, brittle, charcoal-like; black; crustose, split up into large scales; perfect form flat on wood with pore surface exposed, patches several centimeters to decimeters across, (Breitenbach)
Flesh: up to 0.3cm thick but usually less than 0.1cm, corky, faintly zoned; bright yellowish brown, (Gilbertson), corky, faintly zoned; yellowish brown, (Phillips), imperfect form in cross-section spotted dark brown; perfect form with barely developed subiculum, soft and corky when fresh, hard and brittle when dry, (Breitenbach)
Pores: 6-8 per mm, circular, with thick entire walls that become torn, becoming dark reddish-brown; tube layer up to 0.3cm thick, becoming dark reddish brown, brittle, (Gilbertson), 3-5 per mm, angular to elongate; whitish, becoming dark brown; tubes 0.5-1cm long, oblique, usually split in front, (Lincoff), 6-8 per mm, circular, whitish becoming dark brown; tubes 0.3-1cm long, brittle, usually split in front, (Phillips), 3-5 per mm, angular to oblong; "whitish when young, then with a brown gleam, dark brown when old"; tube layer up to 1cm thick, slanting obliquely upward, (Breitenbach)
Odor: indistinct (Buczacki)
Taste: indistinct (Buczacki)
Microscopic: spores 9-10 x 5.5-6.5 microns, broadly elliptic to oval, inamyloid, colorless to pale brownish, illustrated as smooth; basidia 4-spored, 15-18 x 11-12 microns, broadly clavate; setae scattered, scarcely projecting or imbedded, 16-22 x 4.5-7 microns, subulate to ventricose; context hyphae 3.5-7 microns wide, "dark brown in KOH solution, thin- to moderately thick-walled, with frequent branching, simple-septate", trama hyphae "not easily separable, apparently similar", 2.5-3.5 microns wide, (Gilbertson), spores 7-10 x 3.5-5.5 microns, (Breitenbach)
Spore Deposit: white (Buczacki)
Habitat / Range
annual, on Betula (birch), rarely Ulmus (elm), Fagus (beech), Ostrya, causing white rot of heartwood of living birch and rarely other hardwoods, (Gilbertson), imperfect form occurs on trunks of hardwoods, but perfect form with pores and basidia produced under bark only after tree dies, (Breitenbach), year round with new growth in fall (Bacon), spring, summer, fall, (Buczacki)
Similar Species
Inonotus glomerulatus grows on Populus, rarely on other hardwoods, and spores are 5-7 microns long (Ginns(28)). . See also SIMILAR section of Inonotus andersonii.
