34 DELBRUCK 



direct analyses of the contents of the primarily injured and infected 

 cells, a few hours after inoculation, when the first symptoms of infec- 

 tion become microscopically identifiable. This would correspond to the 

 single burst technique of analysis of mixed infection phenomena, 

 which has been the mainstay of the detailed analyses in phage. 



The principal purpose of these remarks is to urge the plant patholo- 

 gists to pursue mixed infection studies on the cellular level, an objective 

 which has proved fruitful in phage beyond any expectation. 



