July 2 4 , i 9 i6 Properties of the Virus of Mosaic Disease 



665 



Iwanowski (12) and, likewise, Beijerinck (4) found that heating the 

 virus to the boiling point destroyed its infectious properties. 



According to Koning (14, p. 71-86), who heated the diluted virus in 

 closed tubes, it remained infective when heated 10 minutes at 8o°, 5 

 minutes at 90 , and 5 minutes at ioo°. 



Woods (20, p. 17-19) believed that the sap of mosaic plants remained 

 infectious to some extent after it had been boiled, owing to the fact that 

 peroxidase was regenerated in the solution. 



The writer's experiments indicate that the infective principle of the 

 virus is quickly and permanently destroyed at temperatures near the 

 boiling point, although such solutions may again show good peroxidase 

 reactions. In these tests, in which the test tube containing the virus was 

 suspended in a beaker of heated water, the virus was kept at room tem- 

 peratures until immersed. The test tube was immersed when the tem- 

 perature in the beaker had begun to exceed the required point. Owing 

 to the small quantities of virus used, the temperatures in all instances 

 were very quickly brought up to the desired height. 



The infective principle of the disease withstands much higher tem- 

 peratures when the dried mosaic leaf material is subjected to dry heat. 

 In the following experiments the air-dried mosaic leaves were finely 

 ground and dried over sulphuric acid in a desiccator from October 8 to 

 the date of heating. For each test 5 gm. of this powdered material 

 were heated in an electric oven, then macerated and extracted with 25 

 c. c. of distilled water. The results shown in Table XII were obtained. 



Table XII. — Effect of heat upon the infectivity of dried mosaic leaf material in 1915, 

 10 plants having been used in each test 



Date 

 heated. 



Period of heating. 



Enzymic reaction after treatment. a f e . lrt ,~ 



Results. 



Oct. 15 

 Do.. 

 Do.. 

 Do.. 

 Do... 



Nov. 5 

 Do... 



l /i hour at go° C 



Yt hour at 100° C 



One hour at ioo° C 



Vk hour at 110° C 



J4 hour at 120 C 



Dry materia!, unheuted . . . 

 Tap water only, unheated 



M hour at 140 C 



Yz hour at 150° C 



Fair peroxidase, Oct. 22 Oct. 



Trace peroxidase, Oct. 22 . . .do. 



... .do . . .do. 



... .do .do. 



No peroxidase, Oct. 22 ... do . 



Fair peroxidase, Oct. 22 do . 



|. ..do. 



No peroxidase, Nov. 10 [ Nov. 12 



do .do 



10 mosaic. 



Do. 

 7 mosaic. 



9 mosaic. 

 7 mosaic. 



10 mosaic. 

 All healthy. 



Do. 

 Do. 



Heating experiments were again carried out, using the virus after it 

 had been evaporated to dryness in small beakers. For each test 40 

 c. c. of undiluted and unaltered virus X 16 were allowed to evaporate by 

 exposure to the air on October 10, 191 5. On November 4 the beakers 

 containing the air-dried residues were heated in an electric oven. After 

 being heated the residues were immediately taken up with 30 c. c. of 

 distilled water. 



