Septal ultrastructure in some genera of the Tremellaceae

Abstract

The fine structure of hyphal septa in the Tremellaceae has shown a number of modifications of the characteristic dolipore–parenthesome type septum. These variations appear of phylogenetic importance and systems of classification have been proposed based upon septal pore structure of a limited number of species. This study reports the fine structure of additional tremellaceous genera, Basidiodendron, Exidiopsis, Sebacina, and Tremellodendron. All species examined have dome-shaped pore caps bounded by unit membrane and with an electron-dense lamella in the pore cap lumen. Pore caps appeared nonperforate in Tremellodendron and Basidiodendron, while narrow discontinuations or distinct perforations were found in Exidiopsis and Sebacina. Thus, their pore cap architecture is similar to that of Exidia and other heterobasidiomycetes with the exception of species of Tremella and members of the Filobasidiaceae. It is suggested that schemes of classification based upon the fine structure of a limited number of taxa may be premature.