Fungi, Ascomycetes, Ustilaginales, Uredinales . contents, the walls 6 82 PLECTOMYCETES [ Fig. 39. Erysipke Polygoni; young perithecium containinguninucleate asci; after Harper. which undergo a change apparently analogous to lignification. \\\ Phyllactiniathe outermost layer, from which the secondary mycelium and the character-istic appendages are derived,consists of thin-walled cells,but in other genera it is notdifferentiated from the pro-tective zone. A single ascus or severalmay be formed in the peri-thecium ; the ascospores,numbering two to eight ineach ascus, begin to developd
Fungi, Ascomycetes, Ustilaginales, Uredinales . contents, the walls 6 82 PLECTOMYCETES [ Fig. 39. Erysipke Polygoni; young perithecium containinguninucleate asci; after Harper. which undergo a change apparently analogous to lignification. \\\ Phyllactiniathe outermost layer, from which the secondary mycelium and the character-istic appendages are derived,consists of thin-walled cells,but in other genera it is notdifferentiated from the pro-tective zone. A single ascus or severalmay be formed in the peri-thecium ; the ascospores,numbering two to eight ineach ascus, begin to developduring the summer or au-tumn, but they remain inthe perithecium under nor-mal conditions and do notgerminate till the beginningof the following year, whenthey are set free by the rupture of the perithecium wall, and produce thefirst infections of the season. In Erysiphc Graminis and Sphaerotheca mors-uvae some of the perithecia separate readily from the mycelium in August,and, if supplied with moisture, will eject their spores after a few hours. Theymay in this way prove a source of infection in
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectfungi, bookyear1922
