Answer the following question given this paragraph: 

Multicellular Photosynthetic Autotrophs hyphae are densely packed so it is difficult to see the individual structures when a mushroom is eaten. However, a mushroom is only a specialised reproductive part of the whole fungus. The main part of the fungi is underground in a whole web of hyphae, called a mycelium. In the mycelium, each fungal cell is separated from each other by a septum. Each fungal cell may have one or more nuclei and remains connected to the mycelium because the septa are porous, allowing cytoplasm to flow through the hyphae and fungal cell walls, made of a hard material called chitin. Some fungi do not have septa, and they appear to be large, branching, multinucleate cells.


Q: A mushroom is only a specialised reproductive part of the whole fungus. the main part of the fungi is underground in a whole web of hyphae, called this?


A:
mycelium