FINE STRUCTURE OF MYCOTA. 7. OBSERVATIONS ON SEPTA OF ASCOMYCETES AND BASIDIOMYCETES

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Abstract
Moore, R. T., and J. H. McAlear. (Cornell U., Ithaca, N. Y.) Fine structure of mycota. 7. Observations on septa of Ascomycetes and Basidiomycetes. Amer. Jour. Bot. 49(1): 86–94. Illus. 1962.—Electron microscopy of 13 carpomycete species (5 Ascomycetes, 5 Basidiomycetes, and 3 Deuteromycetes) presents evidence that suggests there is an Ascomycete‐ and a Basidiomycete‐type septum. The observed Ascomycete septa taper slightly or not at all toward a simple, clear‐channel, central pore, while the observed Basidiomycete septa flare sharply and broadly at the center to produce what is termed a dolipore septum. On each side of this septum is a double membrane structure that is crescent‐shaped in section. This is given the name parenthesome. These dolipore‐parenthesome septa were found to be characteristic of basidiocarpic, dikaryotic, hyphae. Interpretative drawings of both types of septa are presented. From these and the micrographs, it is not difficult to see how materials, including nuclei, could pass through the Ascomycete‐type septum, but it would appear that the modifications of the Basidiomycete‐type septum while maintaining cytoplasmic continuity would prohibit nuclear migration in dikaryotic hyphae. It is postulated that as the plant and animal phylogenetic lines have developed actual diploidism, the terminal group of the fungi may have achieved functional diploidism. Of the 3 species of Deuteromycetes examined, 2, Aspergillus variecolor and Stilbum zacalloxanthum, have typical Ascomycete‐type septa; the third, QM 7739, has Basidiomycete‐type septa. This fungus is a species of Sclerotium, but the present confusion and lack of definitive information regarding the taxonomy, genetics, and perfect stage of this genus prohibit the enlarging at present on the possible significance of this observation.
Funding Information
  • National Heart Institute (H-3493)

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