AMADOU, a soft tough substance once frequently used as tinder, derived from Polyporus fomentarius, a fungus belonging to the group Basidiomycetes and growing upon old trees, espe cially the oak, ash, fir and cherry. The fungus is cut into slices and then steeped in a solution of nitre. Amadou is prepared on the continent of Europe, chiefly in Germany, but the fungus is a native of Britain. Polyporus igniarius and other species are also used, but yield an inferior product.