THE CROWN GALL: TECHNIC 441 



FIG. 337. Crown-gall witch broom on the cultivated carnation due to 

 Bacterium tumefaciens (a natural infection). There was no marked tumefaction 

 at the base of the shoots but, as the sections showed twisted tissues, plates were 

 poured and white colonies were obtained. Six of these were sub-cultured and 

 tested by the writer on Ricinus and tobacco. Colonies 1, 3, 4, 5 and 6 failed 

 to produce any growths, but colony 2 gave sarcomatous tumors on both plants 

 and also on carnation. Photographed November 11, 1916, % nat. size. 



