Mycelium is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates into a monokaryotic mycelium, which cannot reproduce sexually; when two compatible monokaryotic mycelia join and form a dikaryotic mycelium, that mycelium may form fruiting bodies such as mushrooms. A mycelium may be minute, forming a colony that is too small to see, or may grow to span thousands of acres as in Armillaria.
Image: Mushroom's roots (mycélium)
Image: Oyster mushroom (Pleurotus ostreatus) mycelium in petri dish on coffee grounds
Image: 20100916 011605 Mycelium
Image: Mycelium
A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the traditional eukaryotic kingdoms, along with Animalia, Plantae and either Protista or Protozoa and Chromista.
Fungus
Omphalotus nidiformis, a bioluminescent mushroom
Bracket fungi on a tree stump
Widespread white fungus in wood chip mulch in an Oklahoma garden