408 BACTERIUM CAMl'ESTKE IN SOUTH AFRICA. 



Submerged colonies were small, ellipsoid. Numerous feathery 

 X-shaped crystals developed in old agar colonies. 



On potato and cocoanut cylinders standing in water the 

 organism formed a smooth, wet, shining yellow growth. A 

 similar growth was produced on turnip cylinders, but was in 

 this case accompanied by a brown discoloration of the medium. 



( jelatine is slowdy li(|uefied ; in a stab culture the surface 

 becomes liquefied, then the liquefaction extends downward, the 

 solid surface of the gelatine being always more or less horizontal. 



Litmus milk is blued and the casein slowdy thrown down ; 

 it is not coagulated into a stiff mass, and the whey is extruded 

 slowly. 



The optimum temperature for growth is about 30° C, and 

 the death point about 51° C. 



The organism is aerobic, and there is no growth or <ras for- 

 mation in the closed end of fermentation tubes containing beef 

 bouillon and 2 per cent, of the following carbon compounds — 

 dextrose hevulose, saccharose, galactose, lactose, maltose, dex- 

 trin, mannite or glycerin. 



Nitrates are not reduced ; indol is slowly produced in 

 peptonised beef broth and in Dunham's solution. 



Treatment. 



The fact that the organism has been found in a condition 

 capable of producing infection on imported cabbage seed proves 

 the necessity of disinfecting cruciferous seeds before planting as 

 a precautionary measure. For this purpose Smith recommended 

 soaking for 15 minutes in 1:240 formalin, or in i: 1,000 mer- 

 curic chloride. This treatment should kill all organisms pre- 

 sent on the surface of the seed, and it does not affect the 

 germinating power of the seed, as observed in a number of tests 

 carried out in the laboratory. 



Care should also be taken to destroy all diseased rubbish 

 and to avoid land which has borne an infected crop. If insects 

 are numerous, these should be reduced in numbers by the 

 application of some suitable insecticide. 



It has been suggested also that if the water-pore infections 

 occur while the head is forming, the bacteria can be prevented 

 from entering the head by removing leaves or portions of leaves. 

 This treatment might be successful in the treatment of small 

 plots, provided that too large a percentage of the leaves is not 

 removed. 



Summary. 



A disease resembling the black rot of cruciferous plants, 

 described in detail by Dr. Smith, of Washington, is very com- 

 mon in South Africa, but has not, up to the present, been identi- 

 fied as such. 



