1 8 Raymond J. Pool 



Erysiphe graminis DC. 



Usually epiphyllous, sometimes amphigenous ; mycelium sub- 

 persistent, effused or in scattered patches, at first white, later 

 becoming gray or pale brown; perithecia large, 130-280^ in 

 diameter, scattered or gregarious, somewhat depressed, some- 

 times becoming concave, usually immersed in the lanuginose, 

 persistent mycelium ; cells of the perithecium obscure ; appen- 

 dages poorly developed, few or many, very short, sparingly 

 branched, brownish; asci numerous, 10-30, usually about 15, 

 cylindric to ovate-oblong, more or less pedicellate, 70-100 X 

 25-40/x,; spores 8, (sometimes 4) 20-25 X 10-13/x. 



On : Poa pratcnsis, Sccale cereale, Triticum sps. 

 Lincoln, Red Cloud, St. Paul, Wabash, Weeping Water. 



Erysiphe galeopsidis DC. 



On : Stachys pahtstris, ScutcJIaaria lateriflora. 

 Crete, Weeping Water. 



This plant is sometimes described as a distinct species, but for 

 the present I prefer to regard it as a mere form of E. cichoracea- 

 rum. It is very much like E. cichoracearum. It is probable that 

 E. galeopsidis contains only those forms of E. cichoracearum on 

 the hosts named, and on which the spores in the perithecia do not 

 mature on the living host. 



Erysiphe cichoracearum DC. 



Erysiphe lamprocarpa Lev. 

 Erysiphe spadacea B. & C. 



Amphigenous ; mycelium usually evanescent or sometimes sub- 

 persistent and effused, white ; perithecia sub-globose, or globose- 

 depressed, often becoming concave, gregarious or scattered, 80- 

 140^ in diameter, cells variable in size, usually very distinct, 10- 

 20^ wide, sometimes smaller and obscure ; appendages variable, 

 long or short, brown or colorless, numerous, densely interwoven, 

 branched, septate, light or brown throughout, two to four times 

 the diameter of the perithecium; asci numerous, 10-15 or more, 

 variable in size and shape, from narrowly ovate to broadly ovate, 

 or rarely subglobose, more or less pedicellate, 60-90 X 30-50/x ; 

 spores 2, 20-28 X12-20/J,, usually about 24 X H/*- 



On: Ambrosia artcmisiacfolia, A. trifida, A. psilostachya, Aster 

 cricoides, A. nebratskensis, A. laevis, A. multiflorus, A. 

 paniculatus, Cardans altissimus, C. discolor, Bidcns fron- 



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