Postia caesia
Revue mycol., Toulouse 3(no. 9): 19. 1881.
Common Name: none
Synonyms: Oligoporus caesius (Schrad.) Gilb. & Ryvarden; Tyromyces caesius (Schrad.) Murrill; Polyporus caesius (Schrad.) Fries
For descriptions see Gilbertson & Ryvarden, Ginns, Overholts, & 'California Mushrooms'.
Solitary or in small groups on dead conifer wood, sometimes on hardwoods; not uncommon, fruiting from fall through winter, widely distributed.
Unknown.
Postia caesia can by distinguished by relatively small white fan-shaped fruitbodies that are soft and fibrous and stain blue when bruised. It is the only soft, white bracket fungus in California that bruises blue, so it is easily distinguished from other polypores. Specimens of Postia fragilis are similar but where injured turn ochraceous to reddish brown, not blue. Tyromyces chioneus is whitish to grayish, lacks any blue coloration, with a slightly firmer texture.
Recent work has shown that Postia ceasia is not known to occur in North America. A candidate name for our species is Postia simulans (P. Karst.) Spirin & B. Rivoire, but more data/research is needed on western North American collections to clarify the correct name of our species.
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Ginns, J. (2017). Polypores of British Columbia (Fungi: Basidiomycota). British Columbia: Victoria, BC. 260 p. (PDF)
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Miettinen, O., Vlasák, J., Rivoire, B. & Spirin, V. (2018). Postia caesia complex (Polyporales, Basidiomycota) in temperate Northern Hemisphere. Fungal Systematics and Evolution 1(1): 101-129.
Overholts, L.O. (1953). The Polyporaceae of the United States, Alaska, and Canada. University of Michigan Press: Ann Arbor, MN. 466 p. (PDF)
Ryvarden, L. & Melo, I. (2014). Poroid fungi of Europe. Fungiflora: Oslo. 455 p.
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Shen, L., Wang, M., Zhou, J., Xing, J., Cui, B. & Dai, Y. (2019). Taxonomy and phylogeny of Postia. Multi-gene phylogeny and taxonomy of the brown-rot fungi: Postia (Polyporales, Basidiomycota) and related genera . Persoonia 42: 101-126. (PDF)
Closeup of pores
