400 Illinois State Lahoratonj of NaUmd Histonj. 



S. humuli, (DC) Burrill. 



Erysiphe humuli, DC. (Flore Franc, VI., p. 106. 

 Sphierotheca Castagnei, Lev., in part. 



Mostly hypophyllous. Myceliumin conspicuous or evanes- 

 cent; perithecia scattered, abundant, mostly rather small, 75-95;u, 

 wall-texture firm and compact though thin, surface smooth, 

 reticulations small, often obscure, usually less than 15 /a, ; 

 appendages slender, three or more times as long as the diameter 

 of the perithecium, colored throughout when mature, mostly 

 free from the mycelium; ascus broadly elliptical or suborbicu- 

 lar; spores usually 8, large, averaging 20 /* long. 



On Agrimonia Eupatoria: McHenry, Aug. 20, 1183, 1213, 

 Aug. 23, 1249, 1267; McLean, July 2, 2369; Ogle, Sept. 22, 6106 

 (with coleosporium); Adams, July 10 (Seymour). 



This form on Agrimonia has usually been referred to 

 Splwrothexa Castagnei^ hey. (Rabh, Fungi Europ. No. 558; 

 Winter, Die Pilze, II., p. 27; Saccardo, S}^. Fung., I., p. 4; 

 Trelease, Parasitic Fung, of Wis., p. 9; Peck, 29th Rep. N. Y. 

 State Mus., p. 79). A careful examination of American and 

 European specimens on this host and on Potent ilia, show marked 

 differences between them and the typical form of S. Catagnei on 

 various Compositce, etc. They agree, however, with the Euro- 

 pean form on Humnliis (Rabh. Fung. Europ. No. 1049 b). 

 Tulasne (Fung. Carp. Select. I., Tab. IV., 9), under the name 

 of Erysiphe humuli, DC. gives an accurate figure of this form, 

 showing the long, slender, colored appendages and the compact 

 small-celled wall of the perithecium. It seems best, therefore, 

 to revive De Candolle's old species and refer to it the forms on 

 Humidus, Agrimonia, and Potentilla. The perithecia closely 

 resemble those of S. pannosa, but it differs in the larger append- 

 ages and the much less abundant mycelium. 



S. Castagnei, Lev. 



(A.nn. Sci. Nat., Ser. III., Tome XV., p. 139.) 



Mycelium abundant and persistent or sometimes inconspic- 

 uous, occurring on either or both sides of leaves; perithecia 

 abundant, scattered or somewhat aggregated, small, usually 

 about 75 itt, but varying from 60-100 ^\ texture soft, surface un- 

 even, reticulations very large and irregular, 20-30 /w; append- 



