IOWA ACADEMY OF SCIENCE 
21 
On Epilobium coloratum (Muhl.), Ames, Aug. 25, 1894 (Combs); Fayette, 
Aug. 29, 1894 (Fink). 
On Rhus glabra L. Iowa City, X (X) . 
On Rosa arkansana Porter, Ames, 1892 (Carver) ; Decatur Co., Oct., 
1905 (Anderson). 
This species is the destructive hop mildew. In Europe at times 
great losses are sustained by the hop grower through its ravages. 
It is found on the hop in some parts of America but has never been 
reported on that host in Iowa. 
2. Sphaerotheca humuli fulginea (Schlecht), Salmon. 
Sphaerotheca castaguei Lev. in part. Bessey, The Erysiphei, and Prel. List 
Ames Flora. Fink, Blights, etc., of Fayette. Hitchcock. Partial list Iowa 
Powdery Mildews. 
As in S. humuli but the perithecia usually smaller, wall generally 
harder and more brittle; cells larger 20-30 micra or more wide; 
appendages pale to dark brown, usually short. 
On Bidens laevis (L.), B. S. P. Ames, Aug. 25, 1894 (Combs). 
On Bidens frondosa L., Ames, Aug. 22, 1877 (Bessey) ; Aug. 30, 1890 
(Brown) ; Aug. 25, 1894 (Combs) ; *Aug., 1886 (Hitchcock) ; Decatur Co., 
1904 and 1905 (Anderson); Fayette, Sept., 1893 (Fink). 
On Bidens involucrata (Nutt), Britton, Decatur Co., Oct., 1905 (Anderson). 
On Bidens sp., Ames, Oct. 1, 1892 (X). 
On Erechitites hieracifolia (L.), Raf., Ames, Oct. 12, 1878 (Bessey); De- 
catur Co., Oct. 10, 1904 (Anderson) ; Johnson Co., Sept. 16, 1899 (Shimek). 
On Leptandra virginica (L.) Nutt, Ames, Sept. 21, 1878 (Bessey) ; Aug. 27, 
1892 (Carver) ; Decatur Co., 1904 and 1905 (Anderson) ; Iowa City, Aug., 
1888 (Macbride). 
On Leptilon canadense (L.) Britt. *Fayette (X), (Fink). 
On Prunella vulgaris L. Ames, Oct. 17, 1882 (Bessey). 
On Sonchus oleraceus, L. *Fayette (Fink). 
On Taraxacum taraxacum (L.), Karst. Ames, Sept. 4, 1894 (Combs); De- 
catur Co., Oct., 1904 (Anderson) ; Iowa City, Oct. 18, 1886 (Macbride) ; 
Oct. 3 (Bloom). 
The variety is much more common in Iowa than the type. The 
type of the species is seldom collected while the variety is very 
common. Being confined to weeds it works no injury to man in 
Iowa. 
3. Sphaerotheca pannosa (Wallr.), Lev. 
Mycelium abundant on the stem leaves, petiole, calyx, etc., but the peri- 
thecia nearly always occurring on the stem, calyx or petiole, white, becoming 
gray to pale brown. Perithecia more or less immersed in the dense persistent 
mycelium, globose to pyriform, 85-120 micra in diameter, cells about 10 micra 
