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

1. 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.

2. 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.

3. 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.

4. Spore Print

   White.

5. 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

1. Spongipellis fragilis (Fr.) Murrill

2. Polyporus fragilis Fr., 1828

3. Bjerkandera fragilis (Fr.) P. Karst., 1881

4. Leptoporus fragilis (Fr.) Quél., 1888

5. Polystictus fragilis (Fr.) Bigeard & H. Guill., 1913

6. Leptoporus trabeus subsp. fragilis (Fr.) Bourdot & Galzin, 1925

7. Tyromyces fragilis (Fr.) Donk, 1933

8. Spongiporus fragilis (Fr.) A. David, 1980

9. Oligoporus fragilis (Fr.) Gilb. & Ryvarden, 1985

10. Polyporus weinmannii Fr., 1838

11. Polyporus keithii Berk. & Broome, 1875

12. Polyporus vermiculus Veull., 1883

13. Spongipellis sensibilis Murrill, 1912

14. Polyporus kavinae Velen., 1922

15. Polyporus cavinae Velen., 1922

16. Polyporus orbicularis Velen., 1922

17. 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)