38o 



Journal of Agricultural Research 



Vol. XIX. No. g 



chambers for 6 hours to maintain a thin film of moisture around each 

 kernel throughout this period. The subsequent treament with a formaUn 

 solution, I to 400, in sterile tap water was made in the same manner — 

 that is, by pouring the formahn solution on the seeds, draining if off after 

 10 minutes and placing the tubes in moist chambers rinsed with a formalin 

 I to 400 solution. After 6 hours' treatment the seeds were replaced in 

 sterile envelopes, dried overnight, and planted on agar plates. Control 

 seeds, inoculated but not treated, were also planted. Observations were 

 made after 9 to 15 days and are recorded in Table VIII. 



Table VIII. — Effect of 6 hours' presoaking followed byformalin i : 400 treatment on black- 

 chaff bacteria on seeds placed on nutrient agar 



Only 2 out of 1,600 inoculated seeds treated by the presoak method 

 developed typical blackchaff colonies. The controls, which had been 

 inoculated and dried two days, showed 86.6 per cent of the kernels 

 developing the typical colonies when planted on the nutrient agar, thus 

 demonstrating that the absence of growth in the treated seeds was due 

 not to drying of the bacteria but to the treatment as practiced (PI. 79, 80). 

 The presoaking, then, while limiting to a striking degree retardation of 

 seed growth and loss due to failure to germinate, does not reduce the 

 effectiveness of the subsequent formalin treatment as a means of treating 

 diseased seed. In fact, it tends to increase its efficiency in this respect, 

 as will be brought out in the discussion. 



