July 24, 1916 Properties of the Virus of Mosaic Disease 



669 



In another experiment six hornworms which had been feeding upon 

 mosaic plants in the field were transferred to mosaic plants in the labora- 

 tory and left for a day or two. The feces were then collected, macerated 

 with tap water, and tested as follows: Ten plants were inoculated with 

 the extracted sap of mosaic leaves upon which the worms were allowed 

 to feed. Nine plants became mosaic. Ten plants were inoculated with 

 a water extract of the feces of the hornworms. All remained healthy. 

 Ten plants were inoculated with tap water (control). All remained 

 healthy. 



Although these results indicate that the infective principle of the 

 original material had been destroyed by the digestive process of the 

 worms, the feces gave intense peroxidase reactions. 



INFECTIVE PRINCIPLE OF THE DISEASE NOT A NORMAL 

 CONSTITUENT OF THE SAP OF HEALTHY PLANTS 



Woods, from his cutting-back experiments with tobacco and other 

 plants, was led to believe that the mosaic disease of tobacco had its 

 origin within the cells of the plants as a result of abnormal physiological 

 activities. Although Woods ascribed the origin of the disease to peroxi- 

 dase, he believed that there was no essential difference between the 

 peroxidase of healthy and that of diseased plants and came to the con- 

 clusion that this enzym obtained from either source could produce the 

 disease. 



In an earlier paper (1) the writer has adduced evidence to show that the 

 disease is not produced by simply cutting back or otherwise subjecting 

 plants to unfavorable conditions. In the present paper it has also been 

 shown that peroxidase bears no essential relation to infection and that 

 by various methods this and other enzyms may be more or less com- 

 pletely removed from the virus without affecting the infective principle 

 of the disease, and vice versa. 



Although the sap of healthy plants may be rich in oxidase, peroxidase, 

 and catalase, such sap never produces the mosaic disease in healthy 

 plants. Although the peroxidase of diseased plants may be decreased to 

 such an extent by dilution with distilled water that it can not be detected 

 by the guaiac-hydrogen-peroxid test, the solution still remains highly 

 infectious. The results of the experiments in which the virus was diluted 

 with distilled water make this plain (Table XV). 



