328 BACTERIA IN RELATION TO PLANT DISEASES. 



or peptonized Uschinsky's solution; strictly aerobic so far as is known; occasional forma- 

 tion of hydrogen sulphide; partial reduction of litmus in cabbage-broth cultures; slight 

 production of acid on some vegetable media and with various sugars; scanty growth in 

 Fermi's solution, Uschinsky's solution and sometimes in Conn's solution (see Negative) ; 

 feeble growth in vacuo ; killed in agar plates by direct sunlight (30 minutes or less) ; pro- 

 duces a brown pigment soluble in water and a yellow pigment, a lipochrome, insoluble in 

 water but extracted by alcohols, acetone, etc. ; minimum temperature for growth is about 5 

 C., optimum temperature about 30 C., maximum temperature about 38 C to 39 C. Ther- 

 mal death-point is about 51 C. Tolerates sodium hydrate in peptonized beef-bouillon to 

 40, and plant acids to +30 or +40 (?). Young cultures stain readily with various basic 

 anilin dyes; sections of tissues stain satisfactorily with Ziehl's carbol-fuchsin, with nigro- 

 sin and with Heidenhain's or Benda's iron haematoxylin ; a nitro-bacterium according to 

 Fischer's classification (Brenner) see Negative. 



Most of the organisms in a test-tube culture were destroyed by two or three freezings 

 and thawings, but a few individuals survived ten. Killed in one minute by a 0.5 per cent 

 solution of lysol but was not killed in 15 minutes by a 0.25 per cent solution (Harding). 

 Carbolic acid in 0.625 per cent solution killed in 5 minutes, but not in 2 minutes (Harding) . 

 Less sensitive to the presence of sodium chloride than Bad. phaseoli. Remained alive 4 to 6 

 months in agar cultures at room-temperatures (Harding). Lives on culture media for a 

 year in the cool-box (Smith) and on cabbage seed for a year (Harding etal.). Able to 

 live in mixed cultures for a considerable time. Group number 211.3332513 (Smith, 

 Harding). 



NEGATIVE. 



No distinct capsule; no spores; no true pellicle formed on neutral peptonized beef- 

 bouillon (Harding) ; no acid coagulation of milk; occasionally no liquefaction of unfavor- 

 able gelatins; no action on lignified tissues; no solvent action on Swedish filter-paper; no 

 reduction of nitrates to nitrites ; not a nitrobacterium (Smith) ; no characteristic odor ; 

 no production of gas or growth in the closed end of fermentation tubes in peptone-water 

 or peptonized beef-bouillon with any of the following carbon compounds : grape-sugar, 

 fruit-sugar, cane-sugar, galactose, milk-sugar, maltose, dextrin, mannit, glycerin; nor in 

 potato-broth, cabbage-broth or cauliflower-broth; no growth in hydrogen, nitrogen or carbon 

 dioxide; often no growth in Cohn's solution; no growth in peptonized beef-broth over 

 chloroform; brown pigment not formed in beef-broth nor in peptone water with grape- 

 sugar. Not pathogenic to rabbits (Harding). 



TREATMENT. 



The treatment of this disease falls principally under the head of restriction and pre- 

 vention. Seasonal variations undoubtedly play an important part in the development of 

 the disease on lands already infected. Cool, moist lands may be expected to be more sub- 

 ject to it than warm dry ones. Even in the same field the writer has observed the varying 

 quality of the soil to exert a marked influence on the number of water-pore infections, the 

 plants on the dry end of the field being nearly free. In warm autumns accompanied by 

 frequent rains the infections are much more numerous and the disease certainly progresses 

 much more rapidly than in cool, dry seasons. Carman believed the disease to be funda- 

 mentally associated with hot, wet weather. Pammel (1893) says that dry weather in Sep- 

 tember checked the progress of the disease. Russell notes (1898) that the disease varies 

 much in intensity on the same field in different years according to varying weather con- 

 ditions. An intelligent cabbage-grower of Racine, Wisconsin, thoroughly familiar with the 

 black rot, recently told the writer that he lost by this disease the entire crop from a field 

 of six acres in the rainy season of 1900, not having enough cabbages even for the use of his 



