26 
IOWA ACADEMY OF SCIENCE 
affected with the conidial stage but I have been unable to find 
perithecia. 
The cultivated pea (Pisum sativum) is often seriously injured 
by this species. The other Iowa hosts are of but little importance 
economically with the exception of Clematis which is sometimes 
cultivated for ornament. During the seasons of 1904 and 1905 one 
could scarcely find a plant of Polygonum erectum but what was 
more or less affected and thus this weed was largely kept in check 
by the mildew. 
Erysiphe cichoracearum, DC. 
See Plate I. 
Erysiphe cichoracearum, DC. Fink, Blights, etc., of Fayette. 
Erysiphe horridula, Lev. Bessey, The Erysiphei. 
Erysiphe lamprocarpa, Lev. Bessey, The Erysiphei and Prel. List Ames Flora; 
Hitchcock, Partial List Iowa Powdery Mildews; Halsted, in E. & E., N. A. 
Fungi (424). 
Erysiphe linkii Lev. Halsted, in E. & E., N. A. Fungi (1904). 
Erysiphe montagnei Lev. Bessey, The Erysiphei. 
Erysiphe spadacea, Berk & Curt. Bessey, The Erysiphei. 
Amphigenous; mycelium persistent or evanescent, haustoria not lobed; peri- 
thecia gregarious or scattered, 80-140 micra in diameter, very rarely larger, 
cells variable, 10-20 micra wide; appendages variable, generally colored and 
densely interwoven with the mycelium; asci 4-25 or more, more or less stalked, 
58-90x30-50 micra; spores quite uniformly 2, rarely more, 20x28x12-20 micra. 
On Ambrosia artemisiae folia, L. Ames, Sept. 1, 1894 (Combs) ; Decatur Co., 
Aug. 13, 1905 (Anderson) ; * Fayette, 1894 (Fink) ; Iowa City, Sept. 30, 
1886 (Macbride) ; Oct. 6, 1893 (Bloom). 
On Ambrosia trifida, L. Ames, Aug. 25, 1894 (Combs); Sept. 5, 1873 
(Bessey) ; *Aug., 1886 (Hitchcock) ; Decatur Co., Aug., 1904, and 1905 
(Anderson) ; Fremont Co., Aug. 8, 1905 (Anderson) ; * Fayette, 1894 
(Fink) ; Iowa City, Sept. 9, 1885 (Macbride) ; Oct. 7, 1893 (Bloom) ; Ring- 
gold Co., Oct. 7, 1905 (Anderson). 
On Ambrosia trifida integrifolia (Muhl.), T. & G. Ames, Sept. 22, 1894 
(Combs) ; Decatur Co., Sept., 1905 (Anderson) ; Ringgold Co., Oct. 7, 1905 
(Anderson) . 
On Ambrosia psilostachya, DC. *Fayette, 1893 (Fink). 
On Artemisia biennis, Willd. Ames, Sept. 22, 1894 (Combs). 
On Artemisia gnaphaloides, Nutt. Decorah, Sept., 1879 (Holway). 
On Artemisia serrata, Nutt. Ames, Sept., 1887 (Halsted). 
On Aster cordifolius, L., Iowa City, Oct. 11, 1893 (Bloom). 
On Aster laevis L. Armstrong, Sept., 1895 (Shimek) ; Decatur Co., Sept., 
1904 and 1905 (Anderson) ; Fremont Co., Aug. 7, 1905 (Anderson) ; Fay- 
ette, 1893 (Fink). 
On Aster sagittifolius, Willd. Ames, Fall 1889 (X) ; Fayette, 1893 (Fink) ; 
Muscatine, Oct. 21, 1893 (Bloom). 
