Final answer:
The mycelium is composed of a mass of branching filaments called hyphae. Hyphae are thread-like structures that make up the body of a fungus.
Step-by-step explanation:
The mycelium is composed of a mass of branching filaments called hyphae. Hyphae are thread-like structures that make up the body of a fungus. They can fuse with other hyphae to form a mycelium, which is an interconnected mass of hyphal filaments.