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IOWA ACADEMY OF SCIENCE 
ERYSIPHACEAE, Lev. 
Parasitic on living plants. For further description see introduction. 
KEY TO GENERA OF ERYSIPHACEAE. 
Ascus Solitary — 
Appendages of perithecium basal, floccose, similar to the mycelium 
Sphaerotheca 
Appendages of perithecium or some of them dichotomously branched at 
apex Podosphaera 
Asci Several — 
Appendages of perithecium floccose, similar to the mycelium and frequently 
interwoven with it Erysiphe 
Appendages of perithecium uncinate or coiled at apex Uncinula 
Appendages of perithecium dichtomously branched at apex Microsphaera 
Appendages of perithecium rigid, acicular, with a bulbous base. . . .Phyllactinia 
SPHAEROTHECA, Lev. 
Perithecia subglobose, ascus solitary, usually containing eight spores. Ap- 
pendages simple, threads resembling the mycelium and often interwoven with 
it, rarely obsolete. 
Key to Iowa Species of Sphaerotheca. 
Mycelium persistent, thick and dense, with the perithecia more or less im- 
mersed. 
Mycelium white, becoming gray or pale brown 3. S. pannosa 
Mycelium becoming dark brown 4. <S. mors-uvae 
Mycelium evanescent, subpersistent, or persistent, not thick and dense. 
Inner wall of perithecium separating from outer 5. S', phytoptophila 
Inner wall of perithecium scarcely separating. 
Cells of outer wall 10-20 micra wide 1 . S. humuli 
Cells of outer wall 20-30 micra wide 2. <S. humuli fulginea 
1. Sphaerotheca humuli, (DC.) Burrill. 
Sphaerotheca castagnei Lev. in part. Bessey, The Erysiphei and Prel. List 
Ames Flora. Hitchcock, Partial List Iowa Powdery Mildews. Fink, Blights, 
etc., of Fayette. 
Sphaerotheca pruinosa C. & P. Bessey, The Erysiphei. 
Sphaerotheca humuli (DC.) Burr. Fink, Blights, etc., of Fayette. 
Sphaerotheca epilobi (Lk.) Sacc. Fink, in E. & E. N. A. Fungi. 
Amphigenous; mycelium usually evanescent, sometimes persistent, forming 
white spots or patches on the upper surface of the leaf. Perithecia usually 
gregarious, sometimes scattered, 58-120 micra in diameter, cells small, 10-20 
micra wide; appendages very variable as to length and color, sometimes even 
obsolete; ascus broadly elliptical to subglobose, 45-90x50-72 micra, spores 8, 
20-25-12-18 micra. 
On Agrimonia hirsuta (Muhl.) Bicknell, Ames, Oct. 15, 1878 (Bessey) ; 
Fayette. (Fink). 
