848 EXPERIMENT STATION RECORD. 



of a microorganism which is the cause of the bacteriosis of rutabaga, 

 described by L. IT. Parnmel. 1 



The author's attention was first called to the diseases on turnips 

 which were brown rotted internally and usually hollow, the cavities 

 presenting a more or less radial structure. He succeeded in isolating 

 a yellow rod-shaped motile organism, which agreed in most particulars 

 with that described by Pammel. Soon after diseased cabbages were 

 received from Racine, Wisconsin, which were attacked by a microorgan- 

 ism, and the disease bore such a striking resemblance to that on the 

 turnips as to suggest their possible identity. A series of experiments 

 was conducted, which showed that the two diseases were due to the 

 same germ and that they could be produced by cross inoculation. 

 Further study showed that quite a number of cruciferous plants were 

 capable of having this disease induced in their tissue through artificial 

 inoculation. 



One of the most striking symptoms of the disease is a brown or 

 black staining of the tissues occupied by bacteria and, so far as the 

 author's experience goes, the decay induced is that of a sort of dry rot. 

 The disease is peculiarly a vascular one, and the rapid distribution of 

 the bacteria is due to the fact of their motility. Various methods of 

 natural infection were investigated and it was found that the disease 

 could be spread in the greenhouse by slugs and various leaf-eating 

 insects. The water pores at the margins of the leaves were also found 

 to be avenues for infection. The author believes it probable that a 

 majority of the natural infections in the field take place above ground, 

 the disease being transmitted to healthy plants as the result of visits 

 of insects or other small animals, and also that the disease may be 

 transmitted from field to field by the way of the manure pile. He 

 suggests as preventive measures (1) that susceptible plants should not 

 betcultivated on land subject to this disease, (2) the prompt removal 

 of diseased plants, and (3) the destruction of insect enemies and other 

 possible carriers of the disease. 



In the concluding portion of this paper the organism is described, 

 its appearance on beef bouillon, cabbage broth, gelatin, agar, potato, 

 and other media given, and its action in fermentation tubes and its 

 thermal relations stated. 



According to the system of bacteriological nomenclature adopted by 

 the author, the organism was not properly referred by the original dis- 

 coverer and it has been given the name Pseud omonas campestris. It 

 is described as follows : 



"A yellow, rod-shaped, motile microorganism. Size and color varying according to 

 substratum, food supply, etc. Generally 0.7 to 3.0 by 0.4 to 0.5 /i. Oue polar 

 flagellum. Nonsporiferous, so far as known. Pathogenic for various cruciferous 

 plants, entering and dwarfing or destroying the host plant through the vascular 

 system, which becomes decidedly brown. Aerobic but, so far as known, not a gas 



'Iowa Sta. Bui. 27 (E. S. R., (3, p. 998). 



