Stone Mushroom

stone mushroom Polyporus tuberaster, an especially interesting species among the polypores, is the pietra fungaia of (mainly) the central and southern parts of Italy. It occurs elsewhere in Europe but has been less noticed in other countries. Ramsbottom (1932) elucidated the mystery of its nature thus:

Since the earliest times there are references to a stone which, on being watered, gives rise to a mushroom. There are hints of it in many writers, and it is said to be mentioned by Strabo in 50 bc. It appears to have had some connection with the mysteries of the Lynx, and was regarded as the coagulated urine of wolves to be found on the summits of high mountains. The idea was seriously argued in the writings of the Renaissance period.

The stone, as a matter of fact, is a mixture of rock, earth, and pebbles bound together by the mycelium of the fungus Polyporus tuberaster… The stone may be of different sizes and composition, occasionally weighing as much as fifty pounds.