A primordium, often referred to as a knot, is the first point at which the development of a fruit body is visible to the naked eye. Primordia often appear as a balling up of mycelium strands which will eventually develop a cap and a distinct stipe. Primordium may also be referred to as Hyphal Knots. Below are a few pictures for your reference. This article is a . You can help My English Wiki by expanding it.