Postia fragilis
What You Should Know
Postia fragilis is a fairly unremarkable polypore: small, whitish, soft-textured when young, with a matted-tomentose upper surface, and annual fruiting habit. Its most obvious feature, bruising reddish-brown, is mimicked by three other polypores, Parmastomyces transmutans, Amylocystis lapponica and Leptoporus mollis. These species can be separated in the field by their tendency to bruised reddish-brown directly rather than through an intermediate tawny-brown stage. With a microscope Parmastomyces transmutans differs in having dextrinoid spores, Amylocystis lapponica by amyloid cystidia, and Leptoporus mollis by the lack of clamped septate, generative hyphae.
Postia fragilis Mushroom Identification
Fruiting Body
Annual, effused-reflexed, sessile, elongate fan-shaped, 3.0-7.0 cm long, 2.0-3.0 cm wide, 0.5-1.0 cm thick; margin wavy, sometimes over-lapping the tube layer; upper surface white, tomentose, becoming matted in age, azonate, bruising or weathering tawny-brown to vinaceous-brown, eventually dark rusty-brown; context when young soft, white, resilient, up to 0.5 cm thick, discoloring like the upper surface, in age rigid, brownish; odor slightly pungent; taste somewhat bitter.
Hymenophore
Pores 3-4 per mm, whitish, round to angular, bruising vinaceous-brown to reddish-brown, dissepiments thin, becoming torn to dentate with age; tubes 4.0-5.0 mm long, whitish, bruising like the pores.
Spores
4.0-5.0 x 1.0-1.5 µm, cylindrical in face view, sausage-shaped in side-view, smooth, thin-walled, with prominent granular inclusions, hilar appendage not obvious, inamyloid, not dextrinoid.
Spore Print
White.
Habitat
Solitary or in small groups, imbricate or in horizontal lines on conifer logs and branches; fruiting from mid to late winter.
Postia fragilis Synonyms
Spongipellis fragilis (Fr.) Murrill
Polyporus fragilis Fr., 1828
Bjerkandera fragilis (Fr.) P. Karst., 1881
Leptoporus fragilis (Fr.) Quél., 1888
Polystictus fragilis (Fr.) Bigeard & H. Guill., 1913
Leptoporus trabeus subsp. fragilis (Fr.) Bourdot & Galzin, 1925
Tyromyces fragilis (Fr.) Donk, 1933
Spongiporus fragilis (Fr.) A. David, 1980
Oligoporus fragilis (Fr.) Gilb. & Ryvarden, 1985
Polyporus weinmannii Fr., 1838
Polyporus keithii Berk. & Broome, 1875
Polyporus vermiculus Veull., 1883
Spongipellis sensibilis Murrill, 1912
Polyporus kavinae Velen., 1922
Polyporus cavinae Velen., 1922
Polyporus orbicularis Velen., 1922
Daedalea sistotremoides Velen., 1926
Sources:
Photo 1 - Author: Jerzy Opioła (Creative Commons Attribution-Share Alike 4.0 International)
Photo 2 - Author: Jerzy Opioła (Creative Commons Attribution-Share Alike 4.0 International)
Photo 3 - Author: Erlon (Herbert Baker) (Creative Commons Attribution-Share Alike 3.0 Unported)
Photo 4 - Author: James Lindsey (Creative Commons Attribution-Share Alike 2.5 Generic)
