THE CROWN gall: TECHNIC 



433 



Owing to the fact that the parasitic organism occurs in the 

 tissues in comparatively small numbers (very small numbers as 

 compared with tissues subject to any of the diseases previously 

 mentioned), and further to the fact that a large proportion of 

 such as do occur are in a dormant condition, considerable quan- 

 tities of the tumor should be taken for the cultures, and on a 

 portion at least of the plates the inoculations should be very 



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Fig. 331. — Crown gall on Paris daisy showing rod-shaped, mitochondrial 

 (?) bodies photographed in place within the cells. Thin section of a portion of 

 ten tumor cells after treatment with gold chlorid and formic acid and counter- 

 staining with eosin for the nuclei. X 1000. 



heavy (6 to 8 three-millimeter loops) ; moreover, the plates 

 should not be discarded until the end of the third week. Those 

 colonies which come up on the poured plates from the 4th to the 

 8th day or later are more likely to be the organism sought than 

 those which appear during the first three days. The plates 

 may be kept at 20° to 30°C. 



