COWBERRY SCLEROTINIA 153 



stems. Fresh stable manure on the surface of the soil 

 greatly favours the spread of the disease. 



De Bary, Bot. Ztg., p. 458, 1886. 



Potter, Journ. Board Agric., vol. iii. No. 2, figs. 



COWBERRY SCLEROTINIA 



^Sderotinia urnula, Rehm. 

 = Sderotinia vaccinii, Wor.) 



During the early part of summer the leaves and young 

 stems of the cowberry ( Vaccinium vitis-idaea) often show 

 dark-brown patches or stains, which soon become covered 

 with a snow-white delicate mildew, which often assumes a 

 yellowish tinge when old. This mildew, the conidial or 

 summer form of fruit of Sderotinia urnula, when examined 

 under the microscope, is seen to consist of simple or 

 branched chains of conidia, arranged like a string of beads. 

 As the conidia become mature, the narrow neck connecting 

 adjoining conidia undergoes a peculiar change in form and 

 structure, which results in the conidia assuming a lemon- 

 shaped form, and becoming free from each other. The 

 mature conidia have a strong smell, resembling almonds, 

 that proves very attractive to insects, who, along with wind, 

 convey the conidia on to the stigmas of the Vaccinium 

 flowers. These conidia germinate, the germ-tubes passing 

 down the style into the ovary, where the hyphae forms a 

 sclerotium in the interior of the fruit. Such diseased 

 fruits fall prematurely, lie on the ground throughout the 

 winter, and in the spring one or more dark brown, wineglass- 

 shaped ascophores grow from the sclerotium contained 

 within the mummified Vaccinium fruits. 



