240 The Celery-Rot Bacillus 



Scheme (34). After ten days the colour approached "Honey Yellow/' 

 the surface being by that time glistening and smooth. 



The milk-rice was prepared in small petri dishes and in order to 

 obtain exact comparison each plate was inoculated with both organisms, 

 the points of inoculation being about 3 cm. apart ; the growth on 

 this medium was so localized that there was no danger of inter-con- 

 tamination. On these plates the colour was identical with that on 

 potato except on one plate (this probably contained a little less 

 moisture than the rest) where it was "Naples Yellow." 



Although B. carotovorus has been described as a white organism it 

 appears to have been recognized that the colour was not a pure white. 

 Harding and Morse refer to its "creamy growth" and Jones describes 

 a "cream- white layer." Harrison in his description of B. oleraceae, 

 which Harding and Morse find is "clearly identical with Bacillus caro- 

 tovorus," says its growth on potato (Roux's method) is straw-coloured 

 but that there were minor differences in various tests; "thus the 

 growths would be dirty yellow, or honey yellow in colour." 



The method usually adopted by the American phytopathologists 

 when preparing potato cylinders as culture media is to place the half 

 cylinder in an ordinary test tube containing a little water so that the 

 basal portion of the potato is in the water itself ; the whole cut surface 

 remains more moist under these conditions than w^hen a Roux's tube 

 is used. By the latter method development of the organism is more 

 localized and the colour more intense than when the former is employed. 

 In Roux's tubes the yellow colour of the celery bacillus has always 

 been clearly recognized on potato, and the Soyka milk-rice cultures 

 not only confirmed those results but show that Bacillus carotovorus is 

 also a yellow form ; both must therefore be regarded as possessing 

 yellow chromogens. This character in the numerical system of record- 

 ing is represented by -00005 ; the group number of Bacillus carotovorus. 

 Jones, when modified in accordance with this, becomes 221-1113522 

 and the celery-rot organism will then be included under the same 

 number. 



The slight differences to be observed when the two are grown in 

 Uschinsky's solution and on celery extract agar may be due to physio- 

 logical modifications induced by the method of culture subsequent to 

 isolation; in any case it would seem that the form obtained from 

 celery and named by the writer Bacillus apiovorus may at most be 

 only a variety of Bacillus carotovorus Jones. 



