Lei Wan

Lei Wan (雷丸) is the dried sclerotium of Omphalia lapidescens Schroeter (synonym Polyporus mylittae), a parasitic basidiomycete fungus in the Polyporaceae that develops on the roots of bamboo and certain broadleaf trees in southern China. The medicinal substance is the underground sclerotium — an irregular, rounded to ovoid mass 1–3 cm across, with a wrinkled, dark brown to blackish outer skin and a dense, firm, white to pale yellow interior with a granular, somewhat starchy texture. Sclerotia are excavated from the soil during summer and autumn, washed free of debris, and sun-dried. The substance is a fungus, not a higher plant, and has been used since antiquity for parasitic infestations; the active component is a heat-labile protease, so it is administered as a powder rather than in decoction.