PAPERS OX BIOLOGY AND AGRICULTURE 205 



road, about 70 feet from the hedge, was a field of oats. 

 Not a single stalk escaped the rust. A mile farther away 

 was another field of oats which showed an infection of 

 about 75 to 80 per cent. The removal of the hedge has 

 decreased stem-rust losses in this neighborhood in sub- 

 sequent years. 



During the summer of 1922, no serious outbreaks of 

 black stem rust were reported. Weather conditions in 

 June were very unfavorable for the levelopment of stem 

 rust. The rainfall was light and the dry weather hin- 

 dered the growth of the rust. However, the earliest in- 

 fection of stem rust in northern Illinois in 1922 can be 

 traced to barberry bushes, and, if weather conditions had 

 favored stem-rust development, severe attacks with 

 heavy losses might have occurred in that year. 



The first spread of rust from barberries in 1922 was 

 noticed in Lake, Livingston, and Will counties at about 

 the same time. Mr. Thompson found quack grass and 

 oats with a trace of infection near barberry bushes on 

 June 10 in Lake County. In Livingston County on June 

 9, wild barley growing near a barberry hedge was found 

 to be slightly infected. No rust could be found on this 

 grass more than fifty yards away from the hedge. On 

 June 23, barley growing near barberry in McHenry 

 County was heavily rusted, while at a distance of fifty 

 feet from the bushes the rust was extremely light. On 

 the same date orchard grass and quack grass were found 

 rusted near barberry in DuPage County. In almost 

 every instance when infected barberry was found, stem 

 rust was present on grasses or grains, and probably 

 weather conditions alone were responsible for the ab- 

 sence of heavy infections. 



AIRPLANE STUDIES OF THE DISSEMINATION 

 OF STEM-RUST SPORES 



Airplanes have been used in connection with studies 

 of stem-rust spores in the air. 



The purpose of these investigations was to determine 

 general relations which might exist between height or 

 distance from the infected material and the resulting 

 dissemination of rust spores. It includes an attempt to 



