Mass of branched, tubular filaments (hyphae) of fungi (see fungus) that penetrate soil, wood, and other organic matter. The mycelium makes up the thallus (undifferentiated body) of a typical fungus. The mass may be microscopic in size or developed into visible structures, such as brackets, mushrooms, puffballs, or truffles. The mycelium produces spores, directly or through special fruiting bodies.

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