Postia fragilis
Description
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.
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.
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
Photo sources:
Photo 1 - Author: Jerzy Opioła (CC BY-SA 4.0)
Photo 2 - Author: Jerzy Opioła (CC BY-SA 4.0)
Photo 3 - Author: Erlon (Herbert Baker) (CC BY-SA 3.0)
Photo 4 - Author: James Lindsey (CC BY-SA 2.5)