Abstract
The diagnosis of Theissenia is emended to include taxa that lack a definite central perithecial columella and taxa that feature ascospores with a germ slit. Theissenia cinerea is described as a new species that lacks a perithecial columella; T. eurima is described as a new species with ascospores having a germ slit. The type species, T. pyrenocrata, is redescribed and compared with the new species. The taxonomic position of Theissenia is discussed.
This study was supported by National Science Council of R.O.C. Grant NSC90-2311-B-001-066 to YMJ and by US National Science Foundation Grant DEB-9813304 to JDR. The curators of BPI, BR, and K are thanked for loaning specimens and searching for material. We thank Gary J. Samuels, US National Fungus Collections, Beltsville, MD for unpublished information and for type material. We thank Michael J. Adams, Washington State University, for aid with photography and electron microscopy and J. R. Guu, Academia Sinica, for aid with electron microscopy.