I’m trying to come to grips with what a sclerotia is. As a seeker of hypogeous fungi, I have found a few. But never really understood how they became what they were (with the exceptions of hypogeous Hypomyces lactifluorum and Hypomyces chrysospermum).
It seems to me that using the first definition (“comandeered fungal tissue serves as a sclerotium…”) got me thinking along lines of perhaps all Hypomyces grow from sclerotium under Dictionary of Fungi’s definition.
Another thread regarding sclerotia got me started on this train of thought. I know that Psilocybe and Morchella produce sclerotia, but had never thought of Clitocybe much in that regard. Then your observation hit me squarely, and seemingly obviously: another sclerotia! My experience with Helvella lacunosa throughout its life cycle while hunting for truffles gave me first-hand experience in seeing H. lacunosa in many different stages of C. sclerotoidea development. Sometimes the cocooning effect takes several days; sometimes less than a day! Typically the host becomes mummified over a series of several days, and eventually retreats to an underground form. Indeed many of my collections of the sclerotia of C. sclerotoidea were hypogeous to barely epigeous. This lead to the belief that the primordia were being engulfed before any epigeous development.
I also started finding mummified Rhizopogons and Truncocolumella, some of which had been totally consumed and were mere liquidy shells for Hypomyces chrysospermum fruiting, as confirmed by Dr. Trappe. The remains of these sclerotia had already deteriorated beyond the “firm, often rounded stage” and progressed fully into the “firmly integrated into the soil” stage. With Truncocolumella the gleba does something similar to Coprinus comatus, auto-digesting itself into a liquidy mass.