PLATE 79 



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. 377 from South Dakota, dried, and planted on agar without further treatment. 



B. — Sterilized wheat seeds inoculated with isolation No. 377, dried overnight, then 

 soaked in sterile tap water 10 minutes and kept moist 6 hours, then soaked in for- 

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



Note bacterial growth around 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. 



