Ultrastructural Observations on Helvellaceae (Pezizales; Ascomycetes). III. Septal Structures inHelvella

Abstract

Ultrastructure of septa, asci, ascogenous hyphae, and excipular cells of apothecia of selected species of Helvella is described. Electron-opaque, hemispherical structures appear in the basal pores of young asci and with age become more pronounced within the ascus cytoplasm, eventually assuming a dumbbell-shaped appearance. Characteristic electron-opaque and -translucent, V-shaped bands develop within the plug on the ascus side of the pore. An electron-translucent torus separates the pore plug from the septal pore border. Similar pore structures are also found in ascogenous hyphae. Septal pores of paraphyses and excipular cells possess an electron-opaque, lamellate structure characteristic of other taxa of Pezizales. Unlike pores of asci and ascogenous hyphae, those of paraphyses and excipulum also have typical spherical Woronin bodies. Septal pore structures of asci and ascogenous hyphae are unlike those of the Pezizaceae and Ascobolaceae and, although distinct, are more like those ofthe Aleurieae and Otidieae ofthe humariaceous fungi, especially those of Geopyxis. Phylogenetic aspects of these data are discussed.