New York Agricultural Experiment Station. 243 



germinate only during the summer and autumn of the season in 

 which they are produced; also, owing to the fact that the teliospores 

 are never shed, it is improbable that they are carried, to any extent, 

 on leafless plants. 



Since the discovery of the two pine trees affected with blister- 

 rust the outbreaks of currant rust at Geneva may be satisfactorily 

 explained without assuming that the fungus over-winters on currants. 

 Observations made during the epidemic of 1912 convince us that, 

 in the uredinial stage, Cronartium ribicola readily spreads from one 

 black currant plantation to another over distances of one-half mile. 

 With this in mind it is easy to understand how, under favorable 

 weather conditions, such an epidemic as that of 1912 may have 

 originated with a single pair of diseased pine trees. 



