CONTENTS 



PAGE 



Pre-Zadian conceptions 4 



Life history of Ustilago avenae 4 



Inoculation 4 



Incubation 5 



Infection 5 



Life history of Ustilago levis 6 



Epiphytology "7 



Temperature 7 



Moisture 7 



The Leipzig investigations 8 



Zade's studies, 1922 8 



Arland's studies, 1924 9 



Zade's studies, 1924 10 



Diehl's studies. 1925 10 



Roesch's studies, 1926 11 



Comments on the Leipzig investigations 13 



The Cornell investigations 14 



Blossom infection and seedling invasion 14 



Positional relation of pathogene structures to the oat flower and 



grain 14 



Nature and relative importance of the various pathogene structures 



in the oat flower and grain 16 



Sources of, and methods of selecting, experimental materials . . 16 



Ustilago avenae 16 



Ustilago levis 18 



Experiments and results 19 



Deductions 22 



Ustilago avenae 22 



Ustilago levis 22 



Life-history studies 23 



Inoculation studies 24 



With Ustilago avenae 24 



With Ustilago levis 24 



Incubation studies 25 



With Ustilago avenae 25 



With Ustilago levis 26 



Infection studies 26 



Epiphytological studies 27 



General discussion and conclusions • «*1 



Summary of Cornell investigations 32 



