Nov. 1, 1925 
Bacterial Spot of Cowpea and Lima Bean 
853 
illustrated in Plate 4, C, and were grayish white in reflected light and greenish 
fluorescent in transmitted light. The colonies which emerge after the agar 
surface has dried slightly seem to pile up more conspicuously. Colonies on agar 
that has dried out to some extent have a scalloped margin and sculptured surface, 
as shown in Plate 4, B. Submerged colonies are lens-shaped, white, and very 
small (pi. 4, A). Colonies on the underside of the agar are thin, transparent, 
and greenish fluorescent. The agar is unchanged in color. Only a slight odor 
is noticeable. 
Agar stabs. —In +10 beef-peptone agar, growth along the stab was scanty 
and filiform, and on the surface was restricted but piled up. In potato-dextrose 
agar, growth occurred in the stab along the upper part only, and this was slight; 
but on the surface the growth was abundant, spreading, flat, and dull with a 
rugose zone. Growth on this medium was much more vigorous than on the 
beef-peptone agar. 
Agar slants. —On +10 beef-peptone agar, the growth was moderate, spread¬ 
ing, flat, smooth, and grayish white. On potato-dextrose agar the growth was 
abundant, spreading, flat, dull, finely rugose, and grayish white. The margin 
was entire, with a definite beveled border. There was no change in the color of 
this medium in either case. On lima-bean agar a slight greenish pigmentation 
of the medium occurred. 
Gelatin plates. —In two days flat, circular, white colonies, producing saucer¬ 
shaped zones of liquefaction, were present. Liquefaction had proceeded to 
completion the third day. 
Gelatin stabs. —The liquefaction was napiform in 2 days, infundibuliform in 
3 days, stratiform in 7 days, and complete in 14 days, with a white flocculent 
precipitate. 
Potato cylinders. —On steamed potato cylinders growth was rapid and 
abundant, grayish white, and somewhat iridescent, smooth, and glistening, and 
had spread over all the moist surface of the substratum. There was no change in 
the color of the potato tissue. 
Milk. —Clearing of the milk without coagulation began at the top in 2 days 
and was complete in 33 days. Throughout this period the cleared liquid was 
of a pale greenish-yellow color, and the liquid became viscid or gelatinous in 
consistency. 
Litmus milk. —Pale-blue litmus milk was completely decolorized in seven 
days, but no pink , color appeared. Digestion proceeded as noted above and 
was complete in 26 days. The cleared liquid was slightly yellowish green. 
Brom cresol purple in milk. —Brom cresol purple produces a light bluish 
color in milk and becomes yellow if the hydrogen-ion concentration is increased. 
Seven days after inoculation the color was unchanged, except that it was even 
more purplish in the upper cleared portion. After 21 days the blue color 
remained. Accordingly, there is no acid production in milk. 
Methylene blue in milk. —In this medium a deeper blue color was noted 
at the end of two days, while after seven days the milk was completely decolor¬ 
ized except for the cleared portion at the surface, which was greenish. After 
33 days the color was maize yellow, except for a thin greenish layer at the 
surface. 
Reduction of nitrates. —In fermentation tubes containing 1 per cent 
potassium nitrate in a 2 per cent Difco peptone solution, there was good growth 
in the open arm and none in the closed arm. No gas was formed. At the end 
of a month the liquid in the open arm showed a slightly yellowish green. Test- 
tube cultures in the same medium were tested with Trommsdorf’s reagent at 
14 and 33 days after inoculation, and no nitrites were detected. With Nessler’s 
reagent, a strong positive test for ammonia was obtained. Apparently nitrates 
were not reduced, and ammonia probably was produced from the peptone. 
Carbon metabolism. —To test for acid and gas production with different 
carbon sources, 2 per cent solutions of dextrose, saccharose, maltose, lactose, 
mannite, and glycerin were made up in a 2 per cent Difco peptone solution. 
Cultures were- run in duplicate, first in the ordinary U type of fermentation 
tube and later in a simpler and more convenient type of fermentation tube 
(9, fig. J+7) consisting of a smaller inverted test tube within a larger one, a type 
very satisfactory where it is not necessary to measure the quantity of gas. In 
all cases there was abundant growth in the open arm and none in the closed 
arm. No gas was formed. Titration with N/20 sodium hydroxide at the end 
of 17 days in one series and 33 days in the other revealed no marked change in 
acidity as compared with the sterile control tubes. The lactose and glycerin 
cultures were slightly less acid than the controls in one series. 
