142 



C. A. KNIGHT 



However, Steere (1953) was able to demonstrate distinctive strains of this 

 virus by inoculating the juice from systematically infected plants to a local 



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lesion host and then transferring from individual local lesions back to 

 systemic host plants. Three strains showing distinctive symptoms in Datura 

 stramonium plants are illustrated in Fig. 4. These strains were designated 



