PAPERS OX BIOLOGY AND AGRICULTURE 209 



The cost per bush for the salt and application ranges 

 from ten to fifteen cents. 



Epidemiology studies show that barberry bushes are 

 directly responsible for the early spread of black stem 

 rust to fields of grain. The aecial stage of stem rust was 

 found on barberry bushes in northern Illinois as early 

 as June 10 in 1922. 



Observations made by airplane flights show that in 

 June and July aeciospores were present in the air over 

 infected barberries. Also, these spores were caught in the 

 direction of the prevailing winds from 15 to 20 miles 

 from any known area of infected barberries. From 

 flights made on September 12, 1922, no aeciospores were 

 obtained in the air, but numerous teliospores were 

 caught. 



