PLATE 80 



Effect of presoak method used with formalin i to 400 on blackchaff bacteria: 



A. — Controls, dry -heat sterilized wheat seeds inoculated with blackchaff isolation 

 No. 373 from North Dakota, dried, and planted on agar without further treatment. 



B. — Sterilized wheat seeds inoculated with isolation No. 373, dried overnight, then 

 soaked in sterile tap water 10 minutes, kept moist 6 hours, then soaked in formalin 

 I to 400 for 10 minutes, drained, kept moist 6 hours, dried, and planted. 



Note bacterial growth aroimd untreated seeds and absence of growth in presoaked 

 formalin-treated seeds. Two Petri dishes photographed out of a set of 120 dishes in 

 experiment III on tenth day. 



177286°— 20 6 



