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Species Information
Summary: Features include 1) a perennial fruitbody that is hoof-shaped to flat-projecting or effused-reflexed, 2) cap surface that is brown to blackish, with the rounded margin sometimes yellowish brown, 3) small circular pores that are yellowish brown or grayish brown, 4) growth on oak or other hardwoods, and 5) microscopic characters including ventricose cystidia with elongated slender apices (found also in other members of a Phellinus robustus complex). See comments in the SIMILAR section of Fomitiporia fissuratus which is a competing name for some or all records. The description is derived from Gilbertson(1) except where noted.
In western North America it is found in BC, and it is also known from CA and NM. Reports on conifers in Alaska and BC may have been based on misidentification (Ginns(28)). It occurs in CA, LA, NM, and TX, (Gilbertson(1)). A competing name for some or all the records of this species in the Pacific Northwest is Fomitiporia fissurata, described in 2016 from California, with supporting material from Arizona, and range extending to New Mexico, (Vlasak(2)).
Cap: up to 12cm x 20cm x 11cm, ungulate [hoof-shaped] to applanate [flat]; sessile or effused-reflexed [lying flat on wood with pores outward but bending out to form a cap]; brown to blackish; becoming incrusted and rimose [cracked], usually sulcate [grooved], bald; "margin concolorous or yellowish brown at first, then faintly tomentose, rounded, fertile below"
Flesh: up to 3cm thick, hard, woody; shining yellowish brown, zonate, core with white radial streaks near point of attachment
Pores: 7-9 per millimeter, circular, with thick, entire dissepiments; yellowish brown or grayish brown; tube layers "distinct, light brownish, becoming whitish within, woody", each layer up to 0.3cm thick
Stem: sessile (without stem)
Odor: indistinct (Buczacki)
Taste: indistinct (Buczacki)
Microscopic: spores 6-8.5 x 5.5-7 microns, nearly round, smooth, dextrinoid, colorless, thick-walled when mature; basidia 4-spored, 11-12 x 8-9.5 microns, broadly ellipsoid, no clamp connection; cystidia usually abundant in hymenium, ventricose with narrow tapered apex (narrow apical part 1.5-2 microns wide), colorless, thin-walled; setae lacking or occasional in some specimens, 18-37 x 5-8 microns, subulate [awl-shaped] to ventricose, thin-walled to thick-walled; hyphae of context of 2 types: 1) 2.5-4 microns wide, brown in KOH, "thick-walled, rarely branched, rarely simple-septate", 2) inconspicuous, 2.5-5 microns wide, colorless, "thin-walled, simple-septate"; hyphae of trama similar
Spore Deposit: white (Buczacki)
Habitat / Range
perennial, most common on Quercus (oak) in southern U.S. (but also on other hardwood genera), near the base of the living trees, (Gilbertson), all year (Buczacki)
Similar Species
See also SIMILAR sections of Fomitiporia robusta, Fomitiporia tsugina, and Phellinus prunicola.
