406 AGBICULTUEAL AND INDUSTRIAL BACTEEIOLOGY 



or viscid. Gelatin is not liquefied. No growth occurs on 

 potato. There is no gas, but acid, from dextrose and sac- 

 charose, and no visible growth in milk. 



Pathogenesis. — The bacteria apparently gain access to 

 the root through injuries, particularly those produced by 

 nematodes. The portion of the beet below ground decays 

 and becomes filled with areas containing an acid, viscous or 

 slimy liquid. 



PSEUDOMONAS CAMPESTEIS 



Synonym. — Bacillus campestris. 



The black rot of cabbage and related cruciferous plants 

 and its causal organisms was first described by Pammel in 

 Iowa, later it was found in many other portions of the 

 United States and of Europe. 



Morphology. — The organism is a Gram-negative rod, 

 slender, 0.4r-0.5 X 0.7-3.0;u. In young cultures, the cells are 

 motile by means of a single polar flagellum. No capsules 

 and no spores are produced. 



Cultural and Physiological Characters. — Growth is 

 abundant upon most culture media. Cultures on solid 

 media are markedly yellow, older cultures are brownish. 

 Growth is moist, slimy and shining. Milk is made alkaline. 

 Gelatin is liquefied slowly. No gas is produced from carbo- 

 hydrates. Indol is developed. 



Pathogenesis. — The bacteria apparently usually enter 

 the leaf through the marginal water pores. The fibro- 

 vascular bundles are invaded and turn dark. Gradually 

 most of the surrounding tissues are destroyed or disorgan- 

 ized. The disease has proved very destructive in many 

 localities. 



PSEUDOMONAS TUMEFACIENS 



Synonym. — Bacterium tuviefaciens. 

 This organism is the specific cause of crown gall, soft gall 

 and hairy root in most of the species of orchard fruits, 



