Septal ultrastructure in Sirobasidium magnum and its taxonomic implications.

The parenthesomes of Sirobasidium magnum (Sirobasidiaceae) are composed of arrays of ampulliform vesicles from whose bases microfibrils connect to bands of striated material in the dolipore orifices. This septal morphology and the associated character of a yeast haplophase are comparable to that found in species of the Tremellaceae and Filobasidiaceae. The similarity of these basic characteristics in these three families supports their separation into the suborder Tremellineae (species of the Tremellales with regular dolipore/parenthesome septa and mycelial monokaryons are grouped in the suborder Exidiineae).