348 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



fermentation zone was observed during the fourteen days of the exper- 

 iment. 



In the incubator at 23 to 26 C. growth began to show after twenty- 

 four hours. In forty-eight hours on December 16, 1908, the growth 

 had increased and was very vigorous and the fermentation zone was 

 just beginning to appear in all of the five cultures as a very faint, 

 whitish line outside the margin of growth. This zone constantly became 

 more evident, and on the fourth day from inoculation was at its best. 

 Further growth was slower and no great change was to be observed 

 during the two weeks of observation. 



Professor Pierce in his study laid stress upon this characteristic to 

 separate the walnut organism from the closely related species, Pseu- 

 domonas campestris. To test this, we secured a culture of the latter 

 organism from Dr. H. A. Harding of the Geneva Experiment Station 

 of New York State. On July 1, 1911, potato slices were inoculated in the 

 same way as has already been described. Black rot of cabbage (Pseudo- 

 monas campestris) and walnut organisms were used. July 5th, the two 

 series of cultures were examined. Both cultures from the incubator at 

 26 to 28 C. showed fine fermentation zone formation. In fact, it would 

 be difficult to distinguish one from the other. The culture of the walnut 

 organism grown in the culture room at a temperature of 20 C. showed 

 very good fermentation zone formation, while that of Pseudomonas 

 campestris was much less developed. Dr. H. A. Harding, in his study 

 of this organism, speaks or a "white margin or halo just outside of the 

 line of growth."* 



Other Solid Media. The organism was also grown on slices of sweet 

 potato, turnip, garden beet and carrot, Irish potato being used as a 

 check. Slices of these vegetables were sterilized for fifteen minutes in 

 the autoclave at 110 C., then inoculated from the same source and 

 grown in the incubator at 23 to 26 C. for several days. After six 

 days there was abundant growth on each of the different vegetables, 

 but nothing characteristic on any of these media except that of the 

 Irish potato where the white fermentation zone appeared, as has been 

 before described. 



Bouillon. On meat peptone bouillon, plus 15 Fuller's scale, the 

 organism grows well, and in forty-eight hours at 18 C. the liquid is 

 uniformly turbid. In seven days there is a slight flocculent precipi- 

 tate at the bottom of tube. A true pellicle has never been observed 

 to form over the surface of this medium, but a ring-like growth 

 develops readily at margin of liquid on the surface of test tube. 



*New York Agricultural Experiment Station, Geneva, Technical Bulletin No. 13. 



