THE GOOSEBERRY MILDEW 93 



upward by the developing spores, which escape through 

 a small opening, in a peculiar, tendril-like mass, the 

 individual spores being held together by a mucilaginous 

 substance. The raising of the cuticle gives the spots a 

 white or grayish tint. The infested leaves become dull 

 brown or yellow in color, and drop off, commencing 

 sometimes by midsummer, and defoliating the bushes in 

 August. Of course, the fruit on bushes so defoliated 

 does not mature properly. Spraying with fungicides, 

 such as the ammoniacal solution of copper carbonate, is 

 recommended to prevent this disease. 



The Gooseberry Mildew 



Sphoerotheca mors-uvce 



For many years it has been impracticable to grow 

 the finer foreign varieties of gooseberries in the United 

 States, on account of their liability to injury by the 

 gooseberry mildew. This fungus usually appears in 

 spring upon the partially developed leaves and buds, 

 first showing as a sparse, cobwebby covering, which, 

 later, is made to appear white and powdery by the pro- 

 duction of the summer spores. The young berries are 

 also attacked, generally being dwarfed and one-sided as 

 they develop. As the summer progresses the infested 

 leaves become brown and dead, and are generally cov- 

 ered with a thick growth of the fungus mycelium. 



With most of parasitic fungi treated of in these 

 pages the mycelium, or vegetative portion of the fungus 

 is internal; that is, it develops inside the outer cuticle 

 of the host-plant, among the cells of leaf, stem or fruit, 

 sending out its fruiting branches when it has completed 

 its growth. But with the class of so-called "powdery 

 mildews," to which the present species belongs, the my- 

 celium is exter7ial, developing on the outside of the 

 host-plant. The mycelium consists of slender white 



