BLACK ROT OF CRUCIFEROUS PLANTS. 



327 



the end of i, 2, 5, 10, and 15 minutes. Lysol in 0.5 per cent solution killed in i minute, but 

 in 0.25 per cent solution it failed to kill in 15 minutes. Carbolic acid in 0.625 per cent solu- 

 tion killed in 5 minutes, but not in 2 minutes. 



The organism is quite sensitive to the presence of sodium chloride, but not as much 

 so as Bacterium phaseoli. It grew very feebly in salted gelatin (o gelatin converted into + 26 

 by adding c.p. HC1). Further comparisons should be made. 



The organism is able to live in mixed cultures for a considerable time (Russell, Smith). 



In agar cultures at room- temperatures Harding states that the organism remained 

 alive from 4 to 6 months. In the cool-box on potato the writer has kept it alive for a year 

 (average temperature about 12 C.). 



Harding injected fresh bouillon cultures (2.5 cc. subcutaneously, 2 cc. intravenously, 

 and 4 cc. subperitoneally) into rabbits with no ill effect other than a temporary loss in 

 weight. 



RESUME OF SALIENT CHARACTERS. 



POSITIVE. 



Pathogenic to Cruciferae, dissolves middle lamella, plugs vessels, forms numerous 

 closed cavities in the host-plant ; in cabbage causes conspicuous black stain in veins of leaf. 

 Short rods with rounded ends, single or in pairs, and 

 occasionally in short chains of 4 or more; sometimes 

 much resembling a coccus (Coccobacillus) when crowded 

 in the plant or in old cultures; sometimes slightly 

 curved or irregular in shape. Long chains or non- 

 septate filaments frequently occur in sugar-rich media. 

 Pseudozoogloeae ; yellow on all media, changing to dirty 

 yellow-brown in the plant and on cruciferous substrata 

 (culture media) ; motile in newly diseased tissues and in 

 young cultures, i -flagellate; very resistant to drying 

 under certain conditions. 



Surface colonies on agar or gelatin rather slow- 

 growing, circular, pale yellow at first, deepening with 

 age, smooth, wet-shining, flat, with distinct margin; 

 buried colonies small and slow-growing; feathery X- 

 shaped crystals of ammonium magnesium phosphate 

 formed in beef-agar after some days; white chemical 

 halo on nutrient agar; gelatin and Loeffler's blood 

 serum liquefied slowly with brownish stain ; colonies on 

 gelatin feebly zoned concentrically. Rate of liquefac- 

 tion depends upon the medium, it may sometimes begin 

 in 24 hours in peptonized beef-broth gelatin (feebly alka- 

 line to litmus) and be completed in 15 days, often slow. 



Growth in stab-cultures is usually best near the surface. Neutral or alkaline media 

 produce the best growth while acids (+40) inhibit or retard it. Copious growth on steamed 

 potato cylinders, filling the fluid in the bottom of the tube with yellow slime and convert- 

 ing it into a solid alkaline mass turning brownish with age ; nearly complete conversion of 

 potato-starch. 



Organism blues litmus milk; it throws down casein slowly, i.e., by a lab ferment; 

 gradual digestion of casein (Smith, Harding); inverts cane-sugar (?); vitality lessened by 

 long cultivation (Harding) ; slow production of indol in sugar-free peptonized beef-bouillon 



Fig. 130.* 



*FiG. 130. Two tubes of bouillon inoculated with Bacterium campeslre: Left, over chloroform (clear); right, 

 check (clouded). Each tube was inoculated on Feb. 12 with a 2 mm. loop of clouded broth. Photographed Feb. 17. 



