Fungi, Ascomycetes, Ustilaginales, Uredinales . ofconsiderable thickness. The Erysiphaceae are propagated during the summer by rather largeoval uninucleate conidia (fig. 38). These are ordinarily produced in rows on simple conidiophores with one ormore basal cells. In the endophyticE. taurica, however, the conidia areborne singly on branched conidio-phores which emerge through thestomata of the host. In the case ofPhyllactinia Cory-lea, which is met with on a largenumber of deciduous trees, variationsoccur in the shape of the conidiaborne on different hosts, and indicatethe existence of morpho
Fungi, Ascomycetes, Ustilaginales, Uredinales . ofconsiderable thickness. The Erysiphaceae are propagated during the summer by rather largeoval uninucleate conidia (fig. 38). These are ordinarily produced in rows on simple conidiophores with one ormore basal cells. In the endophyticE. taurica, however, the conidia areborne singly on branched conidio-phores which emerge through thestomata of the host. In the case ofPhyllactinia Cory-lea, which is met with on a largenumber of deciduous trees, variationsoccur in the shape of the conidiaborne on different hosts, and indicatethe existence of morphological dis-tinctions between the biologicalforms of the species. Before the connection between theconidia and the perithecia of theErysiphaceae was understood, thegeneric name, Oidium, was applied to the former. The name is still usedto indicate the characteristic form of the conidial stage and to describeconidia when the perithecia are unknown. This was the case with thepowdery vine mildew. The conidial form, known as Oidium Tuckeri, became. Fig. 38. Sphaerotheca pannosa Wallr.; conidio-phores and conidia, x ij,o. in] ERYSIPHALES Si prevalent in Europe in 1845-6, but perithecia were not observed till 47 yearslater, when they appeared during two successive seasons in various localitiesin France, and the fundus was identified with the American vine mildew,lJiici>ii(l(i necator, in which perithecia are common. The unusual productionof the perithecia] stage was attributed to the sudden alternation of high andlow temperatures which characterized the seasons in question. The survivalof the fungus in the absence of ascospores has been attributed to the persist-ence of the mycelium, and also to the development of conidia capable ofpassing the winter in the resting state. Fortunately the disease is readilykept in check by the application of appropriate sprays. A very similar case is that of the oak mildew. In or about 1904, oakscrub in England and many parts of Europe became infect
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectfungi, bookyear1922
