mycelium

n. vegetative threadlike part of a fungus, thallus

Mycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or in many other substrates. Mycelia may form fruiting bodies such as mushrooms. A mycelium may be minute, forming a colony that is too small to see, or it may be extensive. "Is this the largest organism in the world? This 2,400-acre site in eastern Oregon had a contiguous growth of mycelium before logging roads cut through it. Estimated at 1,665 football fields in size and 2,200 years old, this one fungus has killed the forest above it several times over, and in so doing has built deeper soil layers that allow the growth of ever-larger stands of trees. Mushroom-forming forest fungi are unique in that their mycelial mats can achieve such massive proportions." (Stamets)
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n. spawn, mass of eggs deposited by an aquatic animal (i.e. fish, frog, etc.)

(n.)
The white threads or filamentous growth from which a mushroom or fungus is developed; the so-called mushroom spawn.
  

Noun
1. the vegetative part of a fungus consisting of a mass of branching threadlike hyphae
(hypernym) plant part, plant structure
(hyponym) sclerotium
(part-holonym) fungus
(part-meronym) hypha