Originally Posted by maynardsdick

In developing an alternative process which is better adapted for large
scale operation, it was found quite unexpectedly that, grown in vitro on
substrates rich in nutritive material, the fungi produce active mycelium and
sclerotia in large quantities and only a very small number of fruit bodies;
on substrates poor in nutrients, however, the familiar fruit bodies are
produced. On an agar medium containing 1.5% by weight of agar, a
concentration of 0.2 to 0.7% by weight of dry substance of malt extract is
the optimum for the formation of fruit bodies, whereas concentrations of 4
to 10% by weight, depending upon the particular fungal species employed, are optimal for the formation of mycelium and sclerotia.