IOWA ACADEMY OF SCIENCE 
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150, sometimes less, %- 2 V 2 times the diameter of the perithecium, simple, 
hyaline, slightly enlarged upward; asci 8-14, rarely less, 55-80x30-40 micra; 
spores 4-6, 20-26x10-15 micra. 
On Populus deltoides, Marsh. Johnson Co., X (X). 
On Populus grandidentata Michx. Columbus Jc., Aug., 1899 (Pammel) ; John- 
son Co., X (Macbride). 
On Populus tremuloides, Michx. *Iowa City, Oct., 1886 (Macbride). 
On Salix amygdaloides Anders., Ames, Aug. 30, 1894 (Combs). 
On Salix discolor, Muhl. Ames, Aug. 15, 1898 (Ball) ; Greenfield, Sept. 18, 
1893 (Stewart); Johnson Co., Oct. 21, 1893 (Shimek). 
On Salix humilis, Marsh. Ames, Sept., 1899 (Pammel). 
On Salix sp. Ames, Oct. 12, 1878 (Bessey) ; *July, 1886 (Hitchcock) ; De- 
corah, Sept., 1879 (Holway) ; Fayette, Sept., 1893 (Fink) ; Johnson Co., 
Aug., 1886 (Hitchcock) ; Mason City, Sept., 1900 (Shimek) ; Rock Rapids, 
Aug. 5, 1896 (Shimek). 
This is a very variable and widely distributed species. The forms 
on Populus and Salix differ somewhat but not enough to justify 
separation. 
Uncinula necator (Schwein.) Burr. 
Uncinula americana, E. C. Howe. Bessey, Prel. List Ames Flora. 
Uncinula ampelopsidis. Peck. Bessey, Prel. List Ames Flora, Hitchcock, Par- 
tial List Iowa Powdery Mildews. 
Uncinula necator (Schwein.), Burr. Fink, Blights, etc., of Fayette. 
Amphigenous, with perithecia usually epiphyllous, sometimes occurring on 
the inflorescence; mycellium evanescent to subpersistent; perithecia more or 
less scattered, 70-128 micra in diameter, cells rather irregular in shape, 10-20 
micra wide, appendages 7-32, 1-4 times the diameter of the perithecium, septate, 
the lower half colored; apex more or less helicoid when mature; asci 4-6, rarely 
more, 50-60x30-40 micra; spores 4-7, 18-25x10-12 micra. 
On Parthenocissus quinquefolia (L), Planch. Ames, Sept. 11, 1882 (Bessey); 
Aug. 17, 1899 (Hume) ; Decatur Co., Sept, and Oct., 1904 and 1905 (Ander- 
son) ; Decorah, Sept., 1879 (Holway) ; Johnson Co., Oct. 23, 1886 (Mac- 
bride) ; Ringgold Co., Oct. 7, 1905 (Anderson). 
On Vitis cordifolia Michx. *Fayette, 1893 (Fink). 
On Vitis labrusca, L. Ames, Aug., 1891 (Pammel) ; Oct. 30, 1891 (Rolfs) ; 
Oct., 1892 (Bettinger) ; Decatur Co., Oct., 1905 (Anderson). 
On Vitis sp . Ames, Sept., 1889 (X) ; Sept., 1890 (Pammel) ; Sept. 12, 1894 
(Combs) ; Fayette, Oct., 1893 (Fink). 
This is the powdery mildew of the grape and is to be distinguished 
from the downy mildew, Peronospora viticola. In Iowa it does not 
appear to be as destructive on the grape as it is on the Virginia 
creeper (Parthenocissus quinquefolia) . On the latter host it is 
frequently quite destructive, as it also appears to be on the grape 
in some regions. In Iowa so far as the writer’s observation indi- 
cates, the Peronospora is more destructive than the Uncinula. 
