What You Should Know
Calcipostia is a monotypic genus of fungi belonging to the family Fomitopsidaceae. The only species is Calcipostia guttulata. It is a rare mushroom with a small to medium annual polypore. Cap fan-shaped, flattish at maturity, white, smooth but with scattered tiny, circular depressions; bruising rusty-brown; pale brown overall in age. Pores are cream-colored. Saprophytic as well as parasitic.
It has a soft, white fruit body. Circular depressions may be filled with liquid when fresh. Pores are very small, circular to angular. Bitter taste.
Habitat solitary or in small clusters on rotting conifer wood; also fruiting at the base of infected live Sitka spruce.
Distributed in the boreal circumpolar coniferous zone of North America, from Arizona to Alaska and east and south of the Appalachians.
Other names: Dråbe-kødporesvamp (Denmark), Drobnoporek łzawiący / Białak łzawiący (Poland).
Calcipostia guttulata Mushroom Identification
Large, 20–150mm broad, extending 30–120mm and relatively thin, 4–8mm thick, semi-circular, elongated, sessile or attached laterally by a tapered part to the substrate; white, with age indistinctly pink zonate, in injured places also turning violet, purple-brown; on the pileal margin and from the tubes of young sporocarps appear guttation drops, which on drying up leave pitted surface.
White, with a deep-blue-green tint, dry also with lilac tint; 4–6 per mm.
It occurs on the stumps of conifers, spruce, pine, less often on deciduous stumps, singly or in overlapping groups. Grows all year round.
Spores 4-5 x 2-2.5 microns, short-cylindric to oblong, smooth, inamyloid, colorless; basidia 4-spored, 15-20 x 5-6 microns, clavate, with basal clamp; cystidia none, cystidioles 13-18 x 4-5 microns, fusoid, not projecting beyond basidia, with basal clamp; hyphae monomitic, hyphae of context with clamp connections, some very thick-walled with a narrow lumen, occasionally nodose-septate, commonly branching opposite the clamp, 4-8(12) microns wide, some with thin to partially thickened walls, with abundant clamp connections and occasional branching, 3-6 microns wide, gloeoplerous hyphae also present, 5-10(14) microns wide, "staining bright red in phloxine, thin-walled, with occasional distorted clamps, sinuous and with constrictions and swellings", hyphae of trama mostly of the thin-walled non-staining type.
Calcipostia guttulata Look-Alikes
Similar in appearance and microscopically. Has a rough cap that usually has small, black dots on the surface.
Has a mild taste, and typically lacks these features of C. guttulata: saucer-shaped depressions, drops of liquid on most fresh fruitbodies, and a faint greenish cast on the pore surface.
Calcipostia guttulata Synonyms
Postia guttulata (Peck) Julich, 1982
Oligoporus guttulatus (Sacc.) Gilb. & Ryvarden
Polyporus grantii Lloyd
Polyporus guttulatus Sacc.
Polyporus maculatus Peck
Polyporus substipitatus (Murrill) Murrill
Polyporus tiliophilus (Murrill) Sacc. & Trotter
Postia guttulata (Peck) Jülich
Spongiporus guttulatus (Sacc.) A.David
Tyromyces guttulatus (Sacc.) Murrill
Tyromyces stipticus subsp. guttulatus (Peck) Domanski, Orlos & Skirg., 1967
Tyromyces substipitatus Murrill
Tyromyces tiliophilus Murrill
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