I'ODOSPHAERA. 



P. myrtillina Schub. on leaves of Vaccinium Mjp'tillm (bil- 

 berry), V. aliijiiwsuin, and Evrpdrnm nifjrinn (crowberry), (U.S. 

 America). 



Erysiphe. 



The perithecia contain several asci, each with two to eij^ht 

 oval hyaline spores. The appendages are like these of Sji/ikh- 

 rotliccit, simple and thread-like. 



Erysiphe graminis D. C. Mould or mildew of grass and 

 wheat. Grass and cereals, especially wheat, often suffer serious 

 damage from this parasite. The mycelium appears on the leaves 

 as white or brownish spots, generally on the upper surface. 

 Colourless conidia (Oidiicm moniliuidcs, Lk.) are produced acro- 

 petally in chains. The somewhat rare perithecia have brown 

 appendages, and contain eight to sixteen asci, with four to 

 eight spores each ; the spores mature in spring as the dead 

 leaves lie on the ground. This mildew has inflicted great 

 loss both in Europe and America. ])usting the threatened 

 crop witli " flowers of sulphur " will 

 proljably check the first stages of an 

 attack, but care in destroying infected 

 crops is by far the most effective 

 prtiventive. 



Erysiphe martii Lev. This fre- 

 ([uents various Leguminosae (clover, 

 Ijeans, vetches, peas, lupines, etc.), 

 Cruciferae, and other plants (Britain 

 and U.S. America). 



Er. umbelliferarum De Bary. 

 Occurs on various Umbelliferae 

 (Britain). 



Er. communis Wallr. on tobacco, also on various Biinun- 

 culaceae, rapilionaceae, etc. (Britain and U.S. America). 



Er. tortilis Wallr. on Cornus samjuinca (Britain and 

 Aineriea). 



Er. galeopsidis D. C. on Labiatae (Ihitain and 

 America). 



Er. cichoriacearum D. 0. on Compositae, Boragineae, 

 also causing considerable damage to cucumbers (Britain 

 U.S. America). 



'2. — Enjtiphe umheUiJc, 

 Germination of a couidiuni («/>) on 

 Anthriscui^ sylvestris. An attacli- 

 ment-disc luis been foimed, and a 

 c:emi-tube liivs penetr.ited t)ie epider- 

 mis to become the first haustorium. 

 (After De Bary.) 



.1 U.S. 



U.S. 



and 

 and 



