Ultrastructure of Ascospore Ontogeny in Aleuria, Octospora, and Pulvinula (Otideaceae, Pezizales)

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Ultrastructural studies were used to help resolve questions as to the recognition and limits of the heterogeneous family Otideaceae (Pezizales). Ascospore ontogeny was examined in species of Aleuria, Octospora, and Pulvinula and compared with that of other members of the order. Stages of ascosporogenesis, including primary wall formation, were similar to those found in other pezizalean genera. An accumulation of electron-dense globules appeared early in the perisporic sac of species of Aleuria and Octospora and contributes directly to formation of the epispore layer. In Pulvinula, there was a late accumulation of small electron-dense granules that was deposited onto the primary wall to form the epispore. A pronounced development of dense granules occurred in the perispore of Aleuria that condensed onto the epispore to form prominent ornaments. In Octospora, the granules degenerated and formed a loose secondary wall separated from the primary wall by an electron-translucent zone. A secondary wall did not develop in Pulvinula, and the epispore layer became the outer spore wall. We conclude that there was not a close correlation in spore ontogeny among the tribes of Otideaceae currently recognized on the basis of light-microscope data.