Fungous diseases of plants . Fig. 102. Nectria Section ok SroRonocHiuM,WITH VouNG Perithecium. (Photograph by E. J. Durand) containing eight elliptical spores, which at maturity become two-celled by a partition which may divide the spore into two some-what unequal parts. The spores are about 14-16 x 5-7/*. In artificial culture the mycelium develops rapidly, and usuallyupon almost any of the nutrient media. Upon canes, stems, orother solid media the tuberculiform stroma is readily conidia and ascospores germinate readily. In such culturesconidia are produced irregu
Fungous diseases of plants . Fig. 102. Nectria Section ok SroRonocHiuM,WITH VouNG Perithecium. (Photograph by E. J. Durand) containing eight elliptical spores, which at maturity become two-celled by a partition which may divide the spore into two some-what unequal parts. The spores are about 14-16 x 5-7/*. In artificial culture the mycelium develops rapidly, and usuallyupon almost any of the nutrient media. Upon canes, stems, orother solid media the tuberculiform stroma is readily conidia and ascospores germinate readily. In such culturesconidia are produced irregularly upon small branches of thehyphae and sometimes abscised more or less directly from large 242 FUNGOUS DISEASES OF PLANTS hyphae as yeast-like conidial cells. The cushion-like masses alsoproduce conidia in quantity, Mayr described certain macroconidiaborne upon small, white stromata preceding the usual cushions onthe canes; but Durand was unable to detect such Fig. 103. Pleonfctria RHROLmENsrs: A Cluster of Perithecia(Photograph by E. J. Durand) Control. It would seem that the most practical method ofcontrol consists in eradicating diseased vines as they appear inthe spring, the habit and color of the affected canes giving thenecessary clue to their presence, XXXIV. EUROPEAN APPLE CANKER Nectria ditissima Tul. Hartig, R. Der Krebspilz der Laubholzbaume, Nectria ditissima Tul. Un-ters. a. d. forstbotan. Institut Miinchen 1 : 109-128. pi. 6. 1880. This disease is apparently widespread in Europe upon theapple, and it is not uncommon in the northeastern United Statesupon the same host. It may also appear on the pear. The fungusseems to gain entrance to the host through wounds, especiallyhailstone bruises. The mycelium penetrates the bark chiefly, but H ASCOMYCETES 243 to some extent the cambium and the young wood. Much of theinjured bark peels off, and as the mycehum is perennial, extendingfurther each season, large cankers may be produced. Uni
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