210 
Journal of Agricultural Research 
Vol. I, No. 3 
Table; IV. — Comparison of the cultural characteristics of Bacterium aptatum and 
Bacterium xanthochlorum —Continued. 
Media. 
Bacterium aptatum. 
Bacterium xanthochlorum. 
Gentian-violet agar. 
Growth of streak much retarded; no 
growth during first 4 days; after 18 
days, moderate growth; medium 
paled. 
Acid reaction in peptonized saccha¬ 
rose, in peptonized galactose, and in 
peptonized dextrose solutions. 
No retardation; copious growth in two 
days; blue in color; medium greened. 
Alkaline reaction in peptonized saccha¬ 
rose solution; acid reaction in pep¬ 
tonized galactose and in peptonized 
dextrose solutions. 
Fermentation tubes. 
SUMMARY 
1. The leaf-spot diseases of sugar beet and nasturtium described in 
this paper are due to a bacterial organism. 
2. The two diseases occurred during the same summer. The causal 
organism was isolated in pure cultures from both hosts and proved 
infectious to sugar-beet and nasturtium leaves interchangeably. 
3. It is proved from cultural, morphological, and inoculation tests that 
the organisms causing these leaf-spot diseases on both hosts are identical. 
4. The organism is also infectious to bean leaves and pods, lettuce, 
pepper, and eggplant. 
5. It probably enters the plant through wounds or by means of insect 
injuries and may be spread by insects. 
6. The organism is a bacterium belonging to the green fluorescent 
group. It is proved to be different from Bacterium xanthochlorum , 
which is pathogenic to potato, and from Pseudomonas tenuis , which has 
been given the same group number. 
7. It is also different from Bacterium phaseoli , although both organ¬ 
isms produce spotting of bean leaves and pods. 
8. The name Bacterium aptatum , n. sp., is suggested. 
DESCRIPTION OF PLATES 
Plate XVII. Fig. 1.—Sugar-beet leaves inoculated with Bacterium aptatum . 
Photographed eight days after inoculation. 
Fig. 2. —Sugar-beet root inoculated with Bacterium aptatum. Photo¬ 
graphed two weeks after inoculation. 
XVIII (colored). Nasturtium leaves showing bacterial leaf spots 10 days after inocula¬ 
tion with Bacterium aptatum. (May, 1909.) 
XIX. Fig. 1.—Bean leaves inoculated with Bacterium aptatum from leaf- 
spot of sugar beet. 
Fig. 2.—Nasturtium leaves inoculated with Bacterium aptatum from 
leaf-spot of sugar beet. 
Fig. 3.—Bean pods inoculated with Bacterium aptatum from leaf-spot 
of sugar beet. 
(Inoculated Nov. 12, 1908; photographed Nov. 25, 1908.) 
