Sl'HAEROTHECA. 



173 



Sphaerotheca (Podosphaera) castagnei Lev. (Britain aiul 

 U.S. America). The Hop-mildew. The mycelium is found on 

 all parts of hop-plants, causing considerable damage, especially 

 when it attacks the young inflorescences. The perithecia have 

 recumbent, brown, simple appendages. This species appears 

 chiefly on various Compositae, Eosaceae (esp. Spiraea Uhnoria), 

 (,'ucurbitaceae, Geraniaceae, etc. Sorauer reports it as very 

 injurious to apple-trees. 



Fio. 70. — ajthaerothtca cusUiai lul ou Spinua L'iiiuina. The white luycelial coatiuy 

 covers every part of the inflorescences. Two specimens are much less deformed 

 than the others, (v. Tubeuf phot.) 



Oidium farinosum Cooke. Attacks young leaves and calyx 

 of apple; it is easily distinguisiied from the oidium-condition of 

 the preceding species.^ 



Sph. mors-uvae B. et C. The Gooseberry-mildew. Is specially 

 injurious to IliJtcs Uva cvispa and other species of liihca in 

 America. Spraying with a solution of potassium sulphide {I oz. 

 in 1 gallon water) at intervals of twenty days is recommended.- 



' Sorauer, Hedtcu/ia, 1889. 



-Halsted (U.S. Deparlmtnt of A(jricidlure, Report for 1887) describes this 

 (Edit.). 



