Birch Conk, Chaga or Clinker Polypore Inonotus obliquus (Fr.) Pilát (illustrated 50% life size) Fruit body sterile conk 25–40cm across; black; deeply cracked, very hard and brittle when dry. Fertile portion 5mm thick, crust-like, thin; dark brown. Tubes 3–10mm deep, brittle, usually split in front. Pores 4–6 per mm, circular; whitish becoming dark brown. Flesh corky, faintly zoned; bright yellowish brown. Spores broadly ellipsoid to ovoid, smooth, 8–10×5.5–7.5¼. Setae present. Habitat beneath the bark or outer layers of wood on living, dead, standing, or fallen trees, erupting into conspicuous black conks, generally on birch, occasionally on other broad-leaved trees; all year. Rare in England, more common in Scotland. Not edible. Note extracts are used to treat cancer; this fungus features in Solzhenitsyn’s The Cancer Ward, in which a tea made from the fungus is drunk daily. The fungus contains inotodiol which has active anti-tumour properties. (Only specimens growing on Birch trees seem to have this property plus betulin). It has also been shown to have antiviral activity against influenza strains and HIV.
