July 24,1916 Properties of the Virus of Mosaic Disease 



667 



follows: Heated 10 minutes at 85 ° on December 2, 191 4. Cooled at 

 once. A fair peroxidase reaction shown on December 3. Again heated 

 10 minutes at 85 ° on December 4, and cooled at once. Weak peroxidase 

 reaction shown December 5. Again heated 10 minutes at 85 ° on De- 

 cember 5 and immediately cooled. Very weak peroxidase reaction was 

 shown on December 16, when it was again heated for the fourth time for 

 15 minutes at 85 . When used for inoculation on December 28, no 

 peroxidase reaction was shown. The virus was still highly infectious, 

 however, and produced the mosaic disease in 9 out of 10 plants. 



EFFECT OF LOW TEMPERATURES UPON THE VIRUS 



After having been frozen for periods varying from one to four hours 

 at — 12 C, the extracted sap of mosaic plants still retained its infectious 

 properties unchanged. It likewise retained its original virulence after 

 having been exposed outdoors during the entire winter of 191 5 and 

 allowed to freeze and thaw repeatedly. In recent experiments liquid air 

 was used to freeze the virus, and a temperature of approximately — 1 8o° 

 was reached. The results are given in Table XIV. 



Table XIV. — Effect upon iufectivity of freezing fresh mosaic sap to —180° C. by means 

 of liquid air in igi6, 10 plants having been used in each test 



Material used. 



Original virus, unfrozen 



Original virus, frozen Jan. 31 



Duplicate of above 



Tap water and healthy sap, unfrozen 



Time ex- 

 posed to 

 liquid air. 



Minutes. 



Peroxidase reac- 

 tion before freezing. 



Intense, Feb. 1. 



do 



do 



do 



Peroxidase reac- 

 tion after freezing. 



Intense, Feb. 1. 

 do 



Result of inoc- 

 ulating plants, 

 Feb. 2, 1916. 



10 mosaic. 



Do. 



Do. 

 All healthy. 



These tests indicate that the infective principle of the mosaic disease 

 of tobacco is highly resistant to extremely low temperatures. 



DISAPPEARANCE OF PEROXIDASE IN MOSAIC VIRUS WITHOUT LOSS 

 OF INFECTIOUS PROPERTIES 



It has been observed in several instances that unpreserved solutions 

 of virus, as well as dried and ground mosaic material, may lose their 

 peroxidase activities and still retain infectious properties. This hap- 

 pened with dried and ground mosaic leaves bottled in December, 1912. 

 This material showed fair peroxidase reactions on January 28, 191 5, but 

 no reactions for peroxidase in October, 191 5. At this time the virus> 

 still retained the power to produce infection. 



In another instance a bottle of unpreserved virus which was extracted 

 on April 27, 1914, failed to give peroxidase reactions on December 3, 

 1914; yet at this time was highly infectious, producing the disease in 9 

 plants out of 10 inoculated. Thi9 virus was also highly infectious when 

 tested on May 15, 191 5, producing the mosaic disease in 8 out of 10 plants. 

 Although the virus was not tested for peroxidase at the time it was 

 extracted, the fresh virus would probably have shown peroxidase 



