Stamnaria

About

Stamnaria is a genus of fungi in the family Helotiaceae. The genus contains at least 7 species, all of which are parasites of horsetails, reproducing through apothecia which burst through the outer surface of the hosts. It has an anamorph with genus name Titaeospora, but according to current rules the holomorph name Stamnaria should be used where possible.

Summary from Wikipedia