There is a myth that immediately after heavy rains in the forest, mushrooms appear in large numbers and form a very large ring or circle, which may be several metres in diameter. These are called "fairy rings". Can you explain this myth of fairy rings in biological terms? Discuss the mycelial structure in $Agaricus$ and its soil-borne nature.

(N/A) $\rightarrow$ The 'fairy rings' form as the mycelium of the mushroom fungus spreads in the soil from a central point.
$\rightarrow$ It grows peripherally, so that the younger hyphae appear in a circular pattern.
$\rightarrow$ The mycelium of mushrooms absorbs nutrients from the soil.
$\rightarrow$ As nutrients at the center become exhausted, the mycelium expands outward in diameter, forming a circle.
$\rightarrow$ The ring grows in diameter every year, and the mushrooms seen are the fruiting bodies (basidiocarps) of the fungus.
$\rightarrow$ This phenomenon is commonly referred to as a 'Fairy Ring', especially in Europe.