36 



a Appendages simple or more or 

 less flexuoiis, \vithout tip 

 peculiarities. 



b. Appendages usually straight, 

 once or more dichotomously 

 branched at tip, 



c. Appendages usually straight 

 and spirally inrolled at tip, 



Appendages swollen at base 

 so as to form an enlarged 

 plate, 



Erysiphe. 



Microsphaera. 

 Uncinula. 



Phyllactinia. 



THE GOOSEBERRY MILDEW (Sphaerotheca mors-uvae). This 

 species has long been known in the United States. It attacks the leaves 

 and stems, but especially the berries, where it forms dense patches of 

 brown thick -walled mycelium. The fruit thus attacked is practically un- 

 fit for use. It is in this mycelium on the fruit that the perithecia are 

 imbedded. 



Powdery Mildew of Grape (Uncinula Spiralis) . a. winter spore case ; b. ascus ; c. d. k. formation 

 of summer spores. (After Longyear) . 



Control. It is a difficult one to control, but in the Unitied States 

 good results have been obtained by the use of a strong potassium sul- 

 phide spray in the proportion of i oz. to 2 gallons water. Spray about 

 the time the leaves and buds are opening. Repeat every 10 to 12 days 

 if necessary. Some workers recommend Bordeaux Mixture, 4-4-40 formu- 

 la, spraying before the leaves open, after blossoming, and two weeks 

 later. This may discolor the fruit, however. In Canada lime-sulphur has 



