IOWA ACADEMY OF SCIENCES. 
201 
DISEASES OF PLANTS AT AMES, 1894. 
BY L. H. PAMMEL. 
To fully discuss the fungus diseases of plants we should con- 
sider all matters that have a bearing on the question. One of 
the most essential conditions is the character of the weather. 
The relative humidity and precipitation are very important fac- 
tors in the development of fungi. The germination of spores 
depends largely on the humidity of the atmosphere. 
Dr. Erwin P. Smith has shown how important climatic con- 
ditions are in production and spread of Exoascus deformans 
(Berk.) Puckel* * * § and Dr. Byron D. Halsted has shown how 
important a factor moisture plays in the distribution of the 
Downy Mildewsf. Professors B. T. Galloway, H. L. Bolley, 
the writer and numerous others have called attention to the prev- 
alence of wheat rust during certain seasons; and it is a well 
known fact that climatic and meteorological conditions are very 
important factors in the production of these diseases];. 
The writer has published several papers giving the occur- 
rence of fungi for certain seasons. Dr. Halsted has done a sim- 
ilar piece of work for New Jersey and several European 
writers have likewise given lists of fungi for certain years. § 
BACTERIACEAE. 
Bacillus amylovorus (Burrill) Trev. Blight has been unus- 
ually severe this year, occurring on Oldenburg, which seldom 
* Journal Mycology, vol. VI, p. 107. 
tiowa Peronosporeee and a Dry Season, Botanical Gazette, vol. XIII, pp. .52-59. 
Peronosporeae and Rainfall. Journal of Mycology, vol. V, p. 6. Notes upon the Peron- 
osporeae for 1886. Bulletin Department of Botany Iowa Agricultural College, 1886, p. 53. 
$ Journal of Mycology, vol. VII, p. 195. Indiana Agricultural Experiment Station, 
Bulletin No. 26. 
§ L. H. Pammel, Journal of Mycology, vol. VII, p. 95. Agricultural Science, vol. 
VII, p. 30. Botanical Gazette, vol. XVIII, p. 36. Iowa Agricultural Experiment Sta- 
tion .Bulletin No. 18, p. 188. Byron D. Halsted, Notes upon Peronospereae for 1893 
Report Botanical Department of New Jersey Experiment Station for 1893, p. 276. P. 
Magnus, Verzeichniss der vom 11 August bis September in Bayern gesammelten meist 
parasitischen Pilze Separat. Berichte d. Bayrischen Bot. Gesellsch. zur Erforschung 
der heimischen Flora. 
