bacterium campestre in sol'tii africa. 407 



Morbid An atom v. 



This is for the most part a disease of the vascular system, 

 to which in early stages it is contined. The vessels of the fibro- 

 vasciilar bundles, especially the spiral and reticulate vessels, are 

 filled with innumerable bacteria ( hg. i). Hacterial occu- 

 pation of the vessels is followed by the appearance of a brown 

 stain in the walls. The vessels in the softer parts of the plant 

 frecjuently become destroyed, and the bacteria invade the sur- 

 rounding parenchyma (fig. 2). Cavities are formed, 

 frequently involving the whole of the ])ith of the stem in cab- 

 bage, cauliflower, and kohl-rabi, and in turnips the entire root 

 frequently becomes hollow. 



The Parasite. 



The organism causing the cabbage disease in South Africa 

 is undoubtedly Bacterium campestrc (Pam.) Sm. A short 



Ox, 



c 



\ 



Fig. 3. 



resume of the characters of the bacterium isolated from diseased 

 plants will be found to correspond in detail with the characters 

 of B. campcstre as worked out by Smith and other investigators. 



The organism is a yellow schizomycete with a single polar 

 flagellum (fig. 3) ; it is not, as a rule, motile v.'hen taken 

 from the host plant, but is active in young cultures. It occurs 

 singly or in short chains, but most frequently in pairs, and no 

 capsules or spores have been observed. Its extreme measure- 

 ments are .7 — 3 /^ X -4 — -5 /"-, the length being much more 

 variable than the breadth. It stains well with Ellis's modifica- 

 cation of Loeffier's flagella stain, ihc single polar flagellum being 

 two or three times the length of the bacterium. 



The organism is yellow on all media ; on a thinly-sown agar 

 plate (+15 Fuller) kept at 30° C, in five days the organism 

 developed thin. flat, circular yellow- colonies up to 6 mm. 

 diameter. In crowded plates the colonies are much smaller^ 



