174 



Sph. epilobii Lk. occurs on Epilobium (U.S. America). 

 Sph. Niesslii Thiiin. on Sorbus (Pijras) Aria. 

 Sph. pruinosa ( '. et Pk. on Rhus in America. 



Km. 71. Spkaerotkeca custagnei. Epiphytic mycelium on epidermis of Sjiiraea 

 Uimaria. Three haustoria are embedded in epidermal cells. Two conidiophores 

 arc shown, from one of which a conidium has become detached. A hair of 

 .->'/< //-(it ci is shown at one side. (v. Tubeuf del.) 



Podosphaera. 



This genus is distinguished from Sphaerotheca by its upright 

 perithecial appendages, which branch dichotomously towards their 

 extremities. 



Podosphaera oxyacanthae D. C. Apple powdery mildew, 

 also occurring on pear (Pyrus), hawthorn (Crataegus), mountain 

 ash (Pi/rus Aucuparia), and medlar (Mespilus). In America 

 this disease is very injurious to apple-cultivation. 2 It attacks 

 chiefly young seedling plants, stunting their growth and causing 

 them to lose their leaves. 



P. tridactyla "Wallr. This causes injury to leaves of various 

 species of Pr/rn/'s (cherry, plum, and sloe) 3 (Britain and U.S. 

 America). 



-Account by M. B. Waite (U.S. Department of A</ri<_-ii/ture, Report for 

 1888); notes on treatment in Fail-child's experiments (Journal of Mycolof/y, vil. 

 p. 2.")0), and elsewhere (Edit.). 



3 Halsted Zrit-ichrift f. Pflanztnkrankhtiten, 1895, p. 338) gives as additional 

 hosts: Apple, Crataeyu* Oxyacantha, Amelanchier canatlmxi* and Spiraea (Edit.). 



