242 1 VNGOUS DISEASES OF PLANTS 



hyphae as yeast-like conidial cells. The cushion-like masses also 

 produce conidia in quantity. Mayr described certain macroconidia 

 borne upon small, white stromata preceding the usual cushions on 

 the canes ; but Durand was unable to detect such spores. 



FIG. 103. PLEONECTRIA BEROLINENSIS: A CLUSTER OF PERITHECIA 

 (Photograph by E. J. Durand) 



Control. It would seem that the most practical method of 

 control consists in eradicating diseased vines as they appear in 

 the spring, the habit and color of the affected canes giving the 

 necessary 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 the 

 apple, and it is not uncommon in the northeastern United States 

 upon the same host. It may also appear on the pear. The fungus 

 seems to gain entrance to the host through wounds, especially 

 hailstone bruises. The mycelium penetrates the bark chiefly, but 



