| Abstract | While yeasts have been used by man in the baking, wine-making and brewing industries from the beginning of recorded history, it is only comparatively recently that they have been studied systematically as definite species of a group of fungi, and successful efforts at clarification of the relationships among them are more recent still. Yeasts are defined by Alexopoulos as fungi of the class Ascomycetes, subclass Hemiascomycetes; which have a predominantly unicellular thallus; which reproduce asexually by budding, by transverse fission, or both; and which produce ascospores in a naked ascus, originating either from a zygote (formed by conjugation of two gametes) or parthenogenetically from a single somatic cell. Unicellular fungi which do not form spores, which do not obviously belong to some other group, and which otherwise answer to the above description, are also classified as yeasts. |
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