634 Journal of Agricultural Research voi. xm. no. 12 



Saponin in i, 2, 5, 10, and 15 per cent strengths was tested after three 

 days' treatment. The infectivity of the virus was not entirely lost in 

 any of these strengths, but only one or two cases of the mosaic disease 

 resulted in each test, showing that the virus had been greatly weakened 

 in this period. 



Virus treated with naphthalene crystals in excess was highly infectious 

 when tested 16 days later. 



Virus treated with camphor in excess was highly infectious when tested 

 six days later. 



Virus treated with thymol in excess was highly infectious when tested 

 nine days later. 



Antiformin (Eimer & Amend, 1 91 6) in a i per cent strength had greatly 

 weakened the virus after three days' treatment, while 5 and 10 per cent 

 strengths had destroyed the infectivity in the same time. 



Taka-diastase in excess did not appreciably affect the infectivity of the 

 virus after 17 days' treatment. 



Formaldehyde in the concentration of i part in 100 parts of virus 

 solution was used for inoculation 10 minutes, i hour, and 2 hours after 

 being prepared. The infectivity of the virus was greatly weakened, but 

 not wholly destroyed even after 2 hours' treatment. A concentration of 

 I in 100 parts of virus solution had entirely lost its infectivity when tested 

 10 hours later. In other tests formaldehyde in concentrations of i in 

 200, I in 400, I in 600, i in 800, and i in 1,000 parts of virus solution 

 were used for inoculation 18 hours after preparation. The results were 

 as follows : 



I part formaldehyde in 200 parts virus solution All healthy. 



I part formaldehyde in 400 parts virus solution 2 plants mosaic. 



I part formaldehyde in 600 parts virus solution 3 plants mosaic. 



I part formaldehyde in 800 parts virus solution 7 plants mosaic. 



I part formaldehyde in 1,000 parts virus solution 9 plants mosaic. 



Virus untreated 8 plants mosaic. 



Tap water only (control) All healthy. 



A 4 per cent formaldehyde solution of virus was prepared and inocu- 

 lated 10 minutes later and gave three plants mosaic. Inoculations made 

 20 minutes later showed that all infective properties had been destroyed. 

 The original virus gave 10 plants mosaic, and all controls with tap water 

 remained healthy. 



These experiments indicate that the virus of the mosaic disease of 

 tobacco is quickly rendered iimocuous in a 4 per cent strength of formal- 

 dehyde. This strength has been used by the writer to sterilize pots, 

 which were immersed in the solution from 30 minutes to i hour before 

 they were taken out and washed. 



Glycerin appears to affect the infectivity of the virus of the mosaic 

 disease of tobacco only very slowly in the lower concentrations. Very 

 strong concentrations appear to weaken its infectivity noticeably in some 



