668 Journal of Agricultural Research vol. vi. no. i 7 



reactions. In the writer's experience, freshly extracted sap from healthy 

 plants as well as from plants affected with the mosaic disease has never 

 failed to give more or less intense peroxidase reactions. 



Various experiments have shown that talc-treated virus slowly loses 

 its peroxidase activities, although still retaining its infectious properties, 

 as shown in the following test: On November 19, 1915, 50 c. c. of virus 

 X 20 , extracted on November 1, 191 5, and filtered through paper, were 

 mixed to a thick paste with 72 gm. of powdered talc, U. S. P. This 

 material was tested for peroxidase reaction and infectivity from time to 

 time with the following results : 



Strong peroxidase reaction Nov. 19, 1915. 



Very weak peroxidase reaction Nov. 30, 1915. 



Very faint peroxidase reaction Dec. 20, 1915 .... 10 plants mosaic. 



No peroxidase reaction Jan. 18, 1916. ... 4 plants mosaic. 



Similar results have been noted when the virus, and also green mosaic 

 material, have been buried in the soil. The virus, and likewise the green 

 material, may entirely lose their peroxidase activities on decaying, 

 although still retaining the power to produce infection. 



INFECTIOUS PROPERTIES LOST AND PEROXIDASE ACTIVITIES 



RETAINED 



While the infective principle of the mosaic disease appears to be very 

 resistant, the infectivity of a virus solution may be lost under some con- 

 ditions, although the peroxidase is not appreciably changed. This was 

 noted as a result of evaporating a quantity of virus to dryness. A solu- 

 tion of 350 c. c. of virus which had been extracted some time previously 

 and allowed to undergo free fermentation was evaporated at room tem- 

 perature from September 18 to October 21, 191 5. On October 21 the 

 solution had been reduced to 20 c. c. of a thick, heavy, putrid-smelling 

 black sirup. Although this solution gave much more intense reactions 

 for catalase and peroxidase than the original solution, showing that 

 these enzyms had been concentrated during the process of evaporation, 

 the infective principle of the virus had been completely destroyed. 

 Inoculation tests showed that the original virus, however, still retained 

 its infectious properties. 



Although in this instance the infective principle had been destroyed, 

 many tests have shown that the virus of the mosaic disease is not usually 

 destroyed, even when evaporated to dryness. 



Experiments with the feces of hornworms fed upon the leaves of 

 mosaic plants have given rather interesting results. After the worms 

 had been feeding upon the plants for a day or two the feces were col- 

 lected and macerated with distilled water. In one test the feces of a 

 single worm were used. Out of 10 plants inoculated, one plant only 

 became diseased. Since but one case of the mosaic disease appeared 

 in this test, there is a possibility that this plant developed the disease 

 as a result of accidental infection from other sources. 



