Causes of Diseases in Crops 



2. The virus is not inhibited 2. Treatment with either 

 by either chloroform, carbon chloroform, carbon tetrachloride, 

 tetrachloride, toluene, or ace- toluene, acetone or glycerine 

 tone. do not destroy the infectious 



properties. 



2a. The infectious properties 

 are destroyed by concentrations 

 of alcohol which are destructive 

 to enzymes. 



3. The temperatures which 

 destroy the infectious portions 

 are the same as those which affect 

 enzymes or hydrolyze some or- 

 ganic compounds. 



4. Cooling has no more effect 

 on the infectious properties than 

 is exerted on any chemical com- 

 pound, enzyme included. 



5. Properties of the infective 

 principle substantiate the view 

 that the infectious substance is 

 an enzyme and not a virus. 

 This enzyme is not of the nature 

 of the oxidases giving the guaia- 

 cum reaction. 



6. The reproduction of the 

 mosaic enzyme can be accounted 

 for on purely physiological 

 grounds, but the factors which 

 originally induced its formation 

 are still unknown. The con- 

 tinued production of the mosaic 

 enzyme in inoculated plants is 

 in accord with the fundamental 

 principles of pathology and 

 physiology. 



Work of the future will no doubt establish the true 

 cause of mosaic. 



3. The virus is quickly killed 

 at temperatures near the boiling 

 point. 



4. The virus is highly resis- 

 tant to low temperatures at 

 minus 180 C. with liquid air and 

 its infectious properties were not 

 weakened. 



5. The cause of mosaic is 

 not an enzyme. 



6. The virus is a specific 

 particulate substance which is 

 not found in healthy plants. 

 Since this virus is highly infec- 

 tious and is capable of increasing 

 indefinitely within susceptible 

 plants, there is every reason to 

 believe that it is an ultra micro- 

 scopic parasite of some kind. 



