Birch Polypore or Razorstrop Fungus Piptoporus betulinus

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By Roger Phillips

Published 2006

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Birch Polypore or Razorstrop Fungus Piptoporus betulinus (Bull.) P. Karst. (illustrated 35% life size) Bracket 10–20cm across, 2–6cm thick, subglobose, expanding to hoof-shaped, often with a rudimentary stem, margin thick, rounded; whitish when young, becoming fleshy grey-brown with age; upper surface with a thin, separable skin, smooth. Flesh white; rubbery; taste slightly bitter, smell strong and pleasant. Tubes 1.5–5mm long; white. Pores 3–4 per mm, circular; white at first then pale grey-brown. Spores 4.5–6×1.3–1.5¼, cylindrical to bean-shaped. Habitat on birch; all year, annual, but fruit bodies remain intact from one year into the next. Very common. Not edible. Note pieces of this fungus were carried by “Ötzi”, the 5,300-year-old ice mummy found in the Alps in 1991; he may have valued it for its antibiotic properties, but it can also be to used sharpen blades.