Fungi, Ascomycetes, Ustilaginales, Uredinales . iphaceaeand Perisporiaceae show severalpoints in common both with thePlectascales, from which theydiffer in the regular arrangementof their asci, and with the Pyre-nomvcctes, from which they arefor the most part distinguishedby the absence of an ostiole. Their taxonomic position isprobably somewhere betweenthese two groups, and they have,under various systems of classifi-cation, been placed in closer proxi-mity sometimes to the one andsometimes to the other. Their in-clusion here in the Plectomycetesis due to the fact that they, orrather their be
Fungi, Ascomycetes, Ustilaginales, Uredinales . iphaceaeand Perisporiaceae show severalpoints in common both with thePlectascales, from which theydiffer in the regular arrangementof their asci, and with the Pyre-nomvcctes, from which they arefor the most part distinguishedby the absence of an ostiole. Their taxonomic position isprobably somewhere betweenthese two groups, and they have,under various systems of classifi-cation, been placed in closer proxi-mity sometimes to the one andsometimes to the other. Their in-clusion here in the Plectomycetesis due to the fact that they, orrather their best-known family,the Erysiphaceae, show indica-tions of being a primitive simple type of male andfemale organs, the latter withouta trichogyne, and the simplestructure of the perithecium are evidence in this direction. The families of the Erysiphales may be distinguished as follows : Aerial mycelium colourless (or white). Perithecia more or less globose without an ostiole, furnished with conspicuous appendages. Conidia of oidium Fig. 37. Terfezia olbiensis Tul.; section throughhymenium, showing asci irregularly arranged;after Tulasne. • Erysiphaceae. in] ERYSIPHALES 79 Aerial mycelium dark-coloured or rarely absent. Peri-thecia globose or ovoid, without appendages. Conidia not ofoidium type. PERISPORIACEAE. Aerial mycelium dark-coloured or absent. Peritheciaflattened or shield-shaped, with an ostiole at theapex, without appendages. Conidia absent. MlCROTHYRIACEAE. A further and probably important distinction which separates theErysiphaceae from the other two families is the character of the ascus andascospores. In Erysipke and its allies the ascus is more or less globose, thespores are always continuous and colourless, and the number of spores inthe ascus is frequently reduced. In the Perisporiaceae, on the other hand,the ascus is relatively elongated and sometimes cylindrical, and the sporesare commonly two or more celled and often dark-coloured. Most species
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectfungi, bookyear1922
