THE CROWN GALL: NON-NUTRITIONAL ENVIRONMENT 459 



that is, the serum of animals inoculated with it will clump its 

 cultures but will not clump the cultures of the American daisy 

 strain, and vice versa. 



FOR THE DISEASE. Signs. Period of incubation for 

 primary tumor (I have observed well-developed small galls on 

 the peach 18 days after needle puncture (Fig. 318), on the al- 

 mond in 10 days; and beginnings on the daisy in 5 days. 

 Under favorable conditions the beginning of galls on sugar- 

 beets may also be seen as early as the 4th or 5th clay. 



FIG. 349.- Flagellate rods of Bacterium tumefaciens (hop strain) stained 

 by van Ermengem's silver nitrate method. Photomicrographed by the writer. 

 X 1000. 



Time required for the development of secondary tumors in 

 leaves of the daisy? The shortest time I have observed is 10 

 days from the time of stem-inoculation and commencement of 

 the primary stem-tumor. Ordinarily, it is longer. For produc- 

 tion of secondary tumors inoculate into leaf-traces immediately 

 under the petiole in rapidly growing Paris daisy shoots. 



Is the tumor or tumor-strand (which is sometimes visible to 

 the naked eye) green or greenish? How do you account for 

 this? Is it ever brown or brownish? Is it under pressure? 



FIG. 348. Top of Impatiens balsamina (the common garden balsam) showing 

 "hairy-root" due to inoculation on July 26, 1916, with the hop strain of Bacterium 

 tumefaciens. The stem was needle-pricked in the leaf axils. There was much red 

 stain in the tumors and in the roots (red flowered variety) although the leaves 

 and stems of this plant elsewhere were pale green. There was no red stain in 

 tumors on the stems of white flowered balsams inoculated at the same time. 

 Photographed August 22, 1916. Nat. size. 



