654 MINNESOTA BOTANICAL STUDIES. 



20. DIDYMARIA Cord a. Ic. Fung. 6:8. 1854. 

 Sporophores simple or sub-simple, fasciculate, hyaline; con- 



idia acrogenous or acro-pleurogenous on nodulose sporophores, 

 hyaline, elliptical-ovate or broad-oblong, one- septate. 

 4 species reported from the United States. The type is: 



Didymaria didyma (Unger) Pound. Am. Nat. 23:163. 1889. 

 Ramularia didyma Unger Exantb. 169. 1833. 

 Didymaria ungeri Oorda Anleit. Pl.B.f.9,1. 1842. 



Bostrichonema Ces., with simple, erect, spirally flexuous spo- 

 rophores, belongs here. No species are reported for this 

 country. 



21. RAMULARIA Unger. Exanth. 169. 1833. 

 Sporophores fasciculate, simple or with short, scattered 



branchlets, often flexuous, nodulose, or denticulate towards the 

 apex, hyaline or light colored; conidia acrogenous or acro-pleu- 

 rogenous on the denticulations, hyaline, sometimes sub caten- 

 ulate, oblong-cylindrical, typically many-septate, sometimes 

 one- septate or continuous. 



Ovularia and Didymaria are separated from this genus by the 

 shape of the spores. All three, as well as Cercospora are made 

 up of conidial forms of Sphaerella. 



About 60 species are reported for the United States. 



22. CERCOSPORA Fres. Beitraege 90. 1863. 



Virgasporium Cke. Grew 3:182. 1875. 

 Cercosporella Sacc. Mich. "J :20. 1880. 



Sporophores fasciculate, simple, or sometimes sparingly 

 branched, typically fuliginous, but in the sub-genus Cercospo- 

 rella hyaline, flexuous and nodulose or denticulate towards the 

 apex; conidia acrogenous or pleurogenous from tooth-like pro- 

 jections below the apex of the sporophore. pale fuliginous or 

 hyaline, vermiform or elongated cylindrical, usually attenuate 

 above, many-septate. 



Cercospora is closely allied to Ramularia, but is well disting- 

 uished by the shape of the conidia. The conidia are also much 

 longer than in Ramularia. Some species might well be placed 

 in either genus. Including Cercosporella, about 400 species are 

 reported from this country, and more are being described con- 

 tinually. Among the species which we think should be trans- 

 ferred from Ramularia to Cercospora is R. virgaureae Thuem. 

 Journ. Myc. 1 :80. 1885. This would become Cercospora virg- 

 aureae (Thuem.) E. & E. Journ. Myc. 5:69. 1889. 



