Description
Less than 1cm: Use magnifying glass.
Fruit-body crust-like, forming round to oval patches of a few square centimetres to several square decimetres. Upper surface spiny, whitish cream to ochre-yellow, with white, either clearly demarcated or fibrous margin. Spines obtuse to awl-shaped, 3-5 mm long.
Occurrence
Fairly common on trunks and branches of deciduous trees (Birch) in woods with rich soil.
Saprophyte.