140 IOWA ACADEMY OF SCIENCES. 



tory. Professor Trelease thought it probable that the species 

 came from the European cultures. We are therefore inclined to 

 believe with Jordan, Russell, and others that the species is not 

 native in this country. 



FUNGUS DISEASES OP PLANTS AT AMES, IOWA, 1895. 



BY L. H. PAMMEL AND GEO. W. CARVER. 



In previous papers record has been made of the abundance 

 of parasitic fungi for the years of 1891, 1892, 1893 and 1891.^ 

 We hope to continue these observations for the purpose of 

 making comparison. 



Observations from year to year with climatic conditions 

 should make it possible to say how much climate modifies the 

 appearance of disease. Observations in a climate like ours are 

 valuable because of the changeable conditions as to humidity 

 and rainfall. From the nature of the diseases of plants it is 

 difiicult to make exact statements. We must speak in relative 

 terms. In 1893 Puccinia graminis, P. rubigo-vera and P. coronata 

 were very destructive. In 1894 these rusts were not absent, 

 but they were not destructive; in fact, scarce as compared with 

 1893. 



In the study of diseases of plants the condition of the atmos- 

 phere with reference to moisture is an important factor. The 

 universally low humidity of the atmosphere in 1894, no doubt, 

 largely determined the amount of rust that year. So low 

 was the humidity that during the growing season dew was an 

 unusual condition. 



We append table, giving rainfall, relative humidity, 7 a. m. 

 temperature (maximum and minimum), for the months of May, 

 June, July, August and September, taken from the records 

 made at Ames by Dr. J. B. Weems, Mr. W H. Heileman. 



1 L H. Pammel, Jour. Mycology, VII, p. 95. 

 Agricultural Science, VII, p. 20. 

 Proc. Iowa Academy of Science, II, p. 301-203 



