IOWA ACADEMY OF SCIENCES 
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Atlantic Coast to Washington; U. polychaeta upon Geltis occidentalis from 
Carolina to Mississippi and South America; U. confusa Massee. on the 
same host from Carolina; U. geniculata Gerard, on the red mulberry, 
Morus ruora in New York and Illinois; t/. necator (Schw.) Burrili, the 
well known powdery mildew of the grape, and finally U. salicis upon var- 
ious species of Salix and Populus. 
Uncinula salicis (DC.) Wint. 
History. DeCandolle’ described this fungus under the name of Ery- 
siphe salicis, and the form found on poplar was named by the same 
author as E. populi, while Wallroth^ described it as Alphitomorpha adunca 
var. populi. Greville used the name Erysiphe adunca^, and later 
Deveille^ adopted the xidcaiQTJncinula adunca, and by this name it had 
been generally known until Winter^ referred it back to the old DeCandol- 
lean name. 
There are very few economic references to the fungus. Franks Sor- 
aueF and Tubeuf® make brief references to it and Tubeuf has reproduced 
an excellent figure from Tulasne^ 
General Characters. The mycelium is white, prominent, amphigen- 
ous, though usually most abundant on the upper surface, starting from 
definite spots it soon spreads and sometimes covers the entire upper sur- 
face of tne leaf. The perithecia are clustered or scattered, when mature 
black, and maj^ be observed with the unaided eye. 
Microscopic Characters. The mycelium is colorless, thin walled, 
sending lobed haustoria into the epidermal cells; erect conidiophores bear 
the somewhat elongated conidia in chains; perithecia large, from 100-160' 
with small indistinct reticulations; appendages numerous hyaline, bent 
at the tip from once to twice as long as the perithecia; asci usually ovate 
from 5 to 12 or occasionally more, with 'a distinct pedicel, 52-60" x 635-70"; 
spores 22-30 x 15-2" number irom 4-7. In the specimens examined on 
Populus tremuloidcs from the Rocky Mountains there were usually 6, 
22-3" X 1-151". 
Distribution. This fungus is common not only in Europe, but through- 
out the United States. It is more frequently found upon Salix than Popu- 
lus. In the Clear creek country, Colorado, however, it was especially 
abundant upon Populus tremuloidcs and the writer has frequently seen 
it upon P. grandidentata in Iowa. BurrilP*^ reports it upon Populus 
tremuloidcs, P, angulata, P. grandidentata, P. heterophylla, P. balsami- 
fera var. candicans and P. monilifera, and it, the latter host, is recorded 
1. Fl. Fr. 2: 273. 1805 Winter Die Pilze Q: 40. 
FI. Fr. 6: 104. 1815. Bnc. Bot. 8; 220. 
2. Verb. Naturf. Freunde. 1 : 37, 42, Fl. Crypt. Germ. 4 : 755. 
3. Scott. Crypt. Fl. 5 : PI. btp. Note the name as given by Greville in this 
reference is Erysiphe adunca. 
4. Ann. Sci. Nat. III. 15 : 151. PI. G. f. VE. 
5. Die Piize. 2 : 40. 
6. D'ie Frankh. d. Pflanzen, 2: 261. (2 Ed.) 
7. Handh. d. Pflanzenk. 321, 331. 
8. I’fianzciiK. 196. 
9. Selecta Fungorum Carpologia. 198. pi. b. 
10. . 1. c. 
