What structures can be formed by the hardening of fungi mycelium?

Sclerotia are specialized structures formed by the hardening of fungal mycelium, which serve as a survival mechanism for the fungus. They are compact, hardened masses of mycelium that can endure unfavorable environmental conditions. This ability to survive extreme temperatures, drought, or lack of nutrients makes sclerotia particularly important for certain fungi, as they can remain dormant and germinate when conditions improve.

Fruiting bodies, while related to the reproduction of fungi, are formed from the aggregation of hyphae and do not primarily result from the hardening of mycelium. Mycelial clumps arise from the growth and interconnectedness of fungal threads but do not have the same physiological significance or protective function as sclerotia. Hyphal networks refer to the extensive structures formed by branching hyphae that are involved in nutrient absorption but are not hardened or compact structures like sclerotia. Hence, the definition and function of sclerotia as hardened mycelial structures focused on survival make them the correct answer.