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Species Information
Summary: Features include bracket-like or shelf-like whitish fruitbodies often with a rough upper surface, often with small black spots on upper surface, very bitter taste, growth on conifer wood and hardwood, and microscopic characters. The current name in the online Species Fungorum, accessed April 20, 2020, is Amaropostia stiptica, but the current name in Mycobank, accessed the same day, is Postia stiptica. The description is derived from Gilbertson(1) except where noted.
Postia stiptica has been found in BC, WA, OR, ID, MB, NB, NF, NS, ON, AZ, CA, MA, MI, MT, NH, NY, OH, PA, TN, VT, and Europe, (Gilbertson).
Cap: up to 6cm x 11cm x 2cm, bracket-like, or bent outward to form shelf-like cap(s) from pore surface growing flat on wood; dimidiate [semicircular] to elongated; ivory to pale buff, often with small black spots, not zoned; often rough, bald
Flesh: up to 1cm thick, fissile; white, not zoned
Pores: 5-6 per mm, circular to angular, with thin walls that become torn when old; white to ivory; tube layer up to 0.8cm thick, colored as flesh and continuous with it
Odor: strong, indefinite, unpleasant, (Buczacki)
Taste: very bitter
Microscopic: spores 3.5-5 x 1.5-2 microns, "oblong to short-cylindric, some slightly curved", smooth, inamyloid, colorless; basidia 4-spored, 12-19 x 4.5-5.5 microns, clavate, with basal clamp; cystidia absent; hyphae monomitic, hyphae of context 2-5 microns wide, (gelatinizing and swelling to 8 microns wide), colorless in KOH, occasionally branched, thin-walled to thick-walled, with clamp connections, hyphae of trama 2-2.5 microns wide, rather thin-walled, with clamp connections
Spore Deposit: white (Buczacki)
Habitat / Range
annual, single or in small clusters, on dead wood of conifers and hardwoods, associated with brown cubical rot, (Gilbertson), summer to fall (Buczacki)
Similar Species
Calcipostia guttulata is similar microscopically and the small white fruitbodies of P. stiptica with a coarse, usually rough upper surface are the principal basis of separation, (Gilbertson). C. guttulata has a weakly zoned cap with saucer-shaped depressions 0.1-0.3cm in diameter, an exudation of drops of liquid on most fresh fruitbodies, and a faint greenish cast to the pore surface, and it lacks the typical black dots, (Ginns(28)). Tyromyces chioneus has a mild taste, lacks the typical black dots, and is restricted to hardwoods, (Ginns(28)). Postia tephroleuca has longer more narrow slightly curved spores, (Gilbertson).
