PAPERS ON BIOLOGY AND AGRICULTURE 207 



a close estimate of the spores present on each slide. To 

 insure positive identification of all spores, they were 

 measured by means of an ocular micrometer and were 

 compared directly with type slides which contained the 

 various forms. Only spores which were whole and un- 

 injured were counted. In addition to aeciospores, ure- 

 diniospores and teliospores of Puccima graminis Pers., 

 which were the only spores counted, there were, in many 

 instances, large numbers of smut spores, spores of other 

 rusts, pollen grains and spores of a considerable number 

 of other fungi such as Alternaria. 



RESULTS FROM SERIES 1 AND 2 



The slides of this series were exposed on June 14, 

 1922, from an Army airplane over and near the 40-acre 

 area of escaped barberries on the H. C. Lake farm near 

 Gurnee, Illinois. The barberry bushes were infected 

 severely on this date. The wind was blowing from the 

 northeast and the observations were made directly 

 over the area of bushes, at distances of 10, 15, and 25 

 miles south of the area. Each slide was exposed for 

 three minutes. A vaseline-coated slide was placed on 

 one side of the wooden paddle and a slide coated 

 with glycerine jelly on the other; thus, when the paddle 

 was exposed, two slides were in position to catch spores 

 from the air. Observations show that aeciospores were 

 present in the air over the Lake farm at altitudes from 

 100 to 12,000 feet. Urediniospores were found at alti- 

 tudes of 1,000 to 7,000 feet. Ten miles south of this in- 

 fected area, both aeciospores and urediniospores were 

 found at an altitude of 2,000 feet. Fifteen miles south, 

 aeciospores were found at an altitude of 2,000 feet. 

 Twenty-five miles south, only one aeciospore was found 

 and this at an altitude of 2,000 feet. 



RESULTS OF SERIES 3 



Slides of this series were exposed from an Army air- 

 plane over and near the 40-acre area of escaped barber- 

 ries on the H. C. Lake farm near Gurnee, Illinois, on July 

 5, 1922. The length of the exposure was ten minutes. 

 All the slides were coated with vaseline and two slides 



