Tamsiniella labiosa gen. et sp. nov., a new freshwater ascomycete from submerged wood

Investigations into the fungi occurring on wood submerged in freshwater ecosystems have revealed a unique, but characteristic group of fungi. In this paper a new pyrenomycete, Tamsiniella labiosa gen. et sp.nov,, is described and illustrated with light, scanning, and transmission electron micrographs. The germs has remarkable short: stipitate cylindrical asei with an internal refractive apical ring that are apically truncate and have an external thickening. Ascospores are ellipsoidal-fusiform and surrounded by a mucilaginous sheath. At the transmission electron microscope level, the annulus iv of the ascus apical apparatus is differentiated from the inner ascus wail layer and is composed of horizontally oriented, eiectron-dense fibrillar material. A narrow plug is present in the centre of the apical ring. An electron-dense amorphous regk oecurs between the outer ascus wall layer and the annulus part of the apical apparatus. The outer ascus wail layer is lacking a the apex. The ultrastructure of the ascus apex differs from those described in the Lasiosphaeriaceae, Sordariaceae, and Xylariaceae.published_or_final_versio