RHAMNUS IX THE DISSEMINATION OF CROWN RUST. 



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iEcidiospores have been collected on R. cathartica in the vicinity of 

 Madison, Wis., during the past four years, and each year the oats 

 adjoining the hedges have been heavily infected. 



The role played by R. cathartica was demonstrated also at Warren, 

 Minn., by Dr. Henry S. Conard, of Grinnell, Iowa, in July, 1919. A 

 few weeks later further investigations were made at Warren, where 15 



Fig. 6— Two samples of oats from different parts of the same field. 

 The right-hand sample, showing 100 per cent in feet ion with crown 

 rust, was cut adjoining the hedge shown in figures 5 and 7. The 

 left-hand sample came from the distant side of the same field. The 

 intervening oats showed a gradual decrease in percentage of infection 

 and increase in height and she of panicle as the distance from the 

 hedge increased. Photographed July 1, 1921. 



hedges of R. cathartica were studied. The field of oats nearesl to a 

 hedge was about half a mile distant. The rust infection in this field 

 was 90 per cent. Every field of oats inspected within a radius of 10 

 miles was heavily infected with crown rust. Teleutospores were 

 developing on the oats nearest the hedges, while the rust on the oats 

 farther away was only in the uredospore stage. The county agent 



