. - —=— ” ~~ a ae eee re eae 7 a5 i ie Se 
328 BACTERIA IN RELATION TO PLANT DISEASES. 
er 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 Cohn’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 Bact. 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 et al.). 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. Garman 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 
