206 ILLINOIS STATE ACADEMY OF SCIENCE 



find a correlation between distance from infected bar- 

 berries in the direction of prevailing winds and the num- 

 ber of aeciospores or nrediniospores which might be 

 found. 



METHOD USED IN COLLECTING AND EXAMIN- 

 ING THE SPORES 



The work of collecting the spores was made possible 

 through a cooperative agreement between the United 

 States Department of Agriculture and the Air Service 

 of the War Department. Slides were exposed from 

 Army airplanes stationed at Chanute Field, Rantoul, 

 Illinois. The airplanes, piloted by U. S. Army officers, 

 flew from Rantoul to Gurnee, a distance of 150 miles each 

 time spore collections were made. The bushes in the 

 Gurnee area, previously described, were rusted heavily 

 in the spring of 1922 and it was during the period of rust 

 infection on the barberry that most of the flights were 

 made over this area. 



The apparatus as described in another paper 1 consisted 

 of ordinary glass slides 3"xl" in size coated with a very 

 thin film of white vaseline or glycerine jelly. Each slide 

 was fastened to a wooden handle and placed in a small 

 glass bottle two inches in diameter and four inches high. 

 With the use of a close-fitting cork stopper the bottle was 

 made air tight. The glass slide was exposed by removing 

 it from the bottle and holding the handle with the slide 

 attached out in the air above the cockpit of the airplane 

 for a definite time at definite altitudes. The microscopic 

 examination of the slides and germination tests were 

 made in the laboratory. 



Four series of slides were exposed. Glycerine jelly, 

 because it is quite transparent when examined under a 

 microscope, was used in one series to determine its effect- 

 iveness in catching and holding spores. The time of ex- 

 posure varied from three minutes in the first, second and 

 fourth series to ten minutes in the third series. 



In all cases the slides were examined under a micro- 

 scope with a mechanical stage for the purpose of getting 



1 Elvin C. Stakman, Arthur W. Henry, Gordon C. Curran, and "VVarren 

 N. Christopher. Spores in the Upper Air. In Journal of Agricultural Re- 

 search, Vol. 24, No. 6, May 12, 1923. 



