Piptoporus betulinus (Bull. ex Fr.) Karst. syn. Polyporus betulinus Bull. ex Fr. Birkenporling Polypore du bouleau, Birch Polypore or Razorstrop Fungus. Bracket 10–20cm across, 2–6cm thick, subglobose at first, expanding to hoof-shaped often with a rudimentary stem, margin thick and rounded; upper surface with a thin separable skin, smooth, whitish when young darkening to fleshy grey-brown with age. 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, later pale grey-brown. Spores cylindric to bean-shaped, 4.5–6 x 1.3–1.5um. Habitat on birch. Season all year, annual, although fruit bodies remain intact from one year into the next. Very common. Not edible. Distribution, America and Europe.