THE CROWN gall: TYPE 421 



tion on stems and leaves of tobacco, Pelargonium and other 

 plants. 



Earlier than this by some years, Miss Brown and myself had 

 demonstrated that crown galls may bear roots (hairy root of 

 apple, etc.) but I did not then perceive the full meaning and 

 trend of this discovery, viz., that because the type of a crown gall 

 depends on the kind of tissues inoculated it should be just as 

 easy to produce tumors bearing leafy shoots or flower buds as 

 roots. This had to be stumbled upon to be seen, like many 

 another perfectly obvious thing. Its discovery, however, it 

 seems to me, adds very considerably to our knowledge of the 

 nature of crown gall and throws a flood of light also on the origin 

 of animal teratomas. 



The subject of teratomas is so interesting that I have included 

 a number of our more striking results (Figs. 333 to 344 and 347, 

 348). 



The common name ''crown gall" serves to recall the fact 

 that the galls are found very often on the trunks of various fruit 

 trees at the surface of the earth, i.e., on the part known to 

 gardeners as the ''crown" of the plant. They may occur, how- 

 ever, on axiy part of the root or shoot, being very common above 

 ground on the branches of the daisy, grape, quince, apple, rose, 

 willow and poplar. They are also common on the roots of a 

 variety of plants but must not be confused with root galls due 

 to nematodes. 



This disease is common in many localities in North America, 

 Europe, South Africa (Fig. 322), and other parts of the world, 

 and is coming to be recognized in the United States as a more 

 serious disease than it was formerly supposed to be. 



Cause. — Crown gall is due to Bacterium tumefaciens Smith 

 and Townsend. This is a small, white, motile, polar flagellate 

 (Fig. 349), non-sporiferous, Gram negative, non-acid fast, non- 

 liquefying, non-nitrate-reducing, aerobic, non-gas-forming, non- 

 starch-destroying, dry-air-sensitive, sunlight-sensitive, chloro- 



The inoculation was by needle pricks from a 1-day agar-streak culture. Leaves 

 cut away to get a clearer view. Actual size (longest way) of the tumor a little 

 more than 5 inches. Time, 3 months. Tumor larger than the root and still 

 sound, i.e., free from necrosis. 



