PURE CULTURES. b7. 
plate 4 than from the same plant a week later (fig. 10). One would also be more 
certain of pure cultures by plating from the interior of the plant at A, B, or C, 
rather than at X or Y. 
The judgment of experienced bacteriologists as to the pathogenic nature of 
Fig. 10.* 
an organism may toa certain extent be accepted in absence of full proof, but 
only for the time being. Nothing is absolutely certain which has not been experi- 
mentally demonstrated. 
*Fic. 10—Datura metelloides, inoculated by needle-pricks with Bacterium solanacearum, The 
same as plate 4, but six days later, 7. ¢., on July 28. 
