Some common annual polypores
Piptoporus betulinus (Fries) Karsten Birch polypore
Cap: 75-200 mm, kidney-shaped or hoof-shaped, smooth, covered by a thin, separable and greyish silvery or pale brownish skin; cap-margin thick, incurved and projects beyond the tubes.
Stem: rudimentary, simply a small hump below which the fungus develops.
Tubes, pores and spore-print: white.
Spores: sausage-shaped, and thin-walled hyaline under the microscope and very narrow, (5-6 × 1-2 µm). It grows on birch throughout the country where it causes a sap wood-rot which finally converts the inner timber to a red-brown friable mass. The flesh, which contains thickened binding hyphae, is used for mounting insects and for sharpening knives, hence the common name ‘Razor-strop fungus’.
Illustrations: Hvass 269; LH 67; NB 1174; WD 933.
Inonotus hispidus (Fries) Karsten Shaggy polypore
Cap: 100-250 mm, kidney-shaped, yellow-brown to rust-brown, but finally almost black, at first covered with shaggy hairs, but these tend to mat together with age.
Stem: absent.