1923] 



JENNISON — POTATO BLACKLEG 21 



No. 195. Kindness of W. J. Morse. His "IIP." Isolated by him 

 in Maine, Aug., 1908, "from typical blackleg plants". Found by the 

 writer to be pathogenic to potato tubers. Still virulent late in 1917. 

 Used by Morse (17). 



No. 196. B. solanisaprus Harrison. Kindness of W. J. Morse, who 

 used this strain in his studies ('17). The culture was originally pro- 

 cured from S. F. Edwards, Ontario Agr. Coll., in March, 1909. 

 Found by the writer to be pathogenic to potatoes. Virulence in 1917 

 good. 



No. 197. J5. atrosepticus van Hall. Kindness of W. J. Morse. 

 Previously studied by him ('17). This strain Morse "received under 



that name from Krai's laboratory 1 in 1910 At first it showed 



weak pathogenicity to potato tubers, and repeated inoculations to 

 growing stems failed to produce the disease until the present summer 

 [1916]." Found by the writer to be pathogenic, though, if anything, 

 less strongly so than some of the others. Still virulent late in 1917. 



No. 198. 



Murphy. Kindness of W 





Morse, who "received this from Dr. Pethybridge himself in 1911. . . 



. . It also has produced active decay of tubers and blackleg of the 



stem upon inoculation." Used by Morse ('17). I found it to be 



pathogenic. Still virulent in Nov., 1917. 



No. 200. "£. phytophthorus" from Minnesota. Kindness of E. C. 

 Stakman. Isolated 1915. The writer found it to be pathogenic to 

 potato tubers. Still virulent in 1917. 



No. 201. B. phytophthorus Appel. Kindness of B. M. Duggar 

 who obtained the culture from E. F. Smith. The latter procured the 

 strain from Dr. Aderhold in Berlin about 1906. It is presumed that 

 Smith's culture was a transfer from Appel 's original culture. The 

 writer found it to be pathogenic. Still virulent in 1917. 



No. 202. "5. solanisaprus/' Kindness of D. H. Jones who wrote 

 that "the transfer purports to be from original strain of J5. solanisap- 

 rus . 4 . . received in Oct., 1916, from the American Museum, to 

 which Dr. Harrison had formerly sent a culture." Found by the 

 writer to be pathogenic. Still virulent in late 1917. 



II. Comparative Studies of Causal Organisms 



Invigoration of cultures. — The cultures used by the writer 

 were growing on beef agar at the time the comparative studies 

 presented below were begun. Some had been previously culti- 

 vated on agar and some in nutrient broth for greater or less 

 length of time. To begin with, all were plated out to insure 

 purity of the culture and then each one was invigorated by trans- 



1 Krai's Bakteriologisches Laboratorium, Prague, Austria. 











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