Dec. io, 1913 
Disease of Sugar-Beet and Nasturtium Leaves 
197 
Agar Plates. —At a temperature of 20° to 24 0 C. the colonies on 
peptonized beef agar (+15 on Fuller's scale) are up in 24 to 36 hours 
when plates are poured from a young bouillon culture. They are round, 
smooth, flat, glistening, 1 to 2 mm. in diameter, with entire edge, fish¬ 
scalelike markings, whitish in reflected light, bluish in transmitted light. 
In three days the colonies are 4 to 5 mm. in diameter on plates thinly 
sown, and the agar has changed to a faint yellowish green color. In 7 
to 10 days the colonies are a deep-cream color. 
Agar Stroke. —There is a moderate growth along the stroke in 24 
hours. It is whitish, flat, smooth, and glistening, spreading at base. In 
two days there is a heavy growth; in four days the agar has changed 
to a slight yellowish green, with the growth of a viscid consistency. In 
from five to seven days the bacterial growth covers nearly the entire 
surface of the agar, densely clouds the condensation water, and becomes 
slightly malodorous. The greatest growth of the organism occurs at the 
base of the stroke and in the condensation water. The margin of the 
stroke is often scalloped, with some edges of the scallop thinner than 
others. The growth on old cultures is a deep-cream color, the medium 
having become brown. 
Tests made with the same organism, transferred at intervals for 
several years to artificial media, showed that the greenish color was not 
always produced in agar. 
Agar Stab. —Growth is slow in stab culture, only a slight trace occur¬ 
ring in two days. It is best at the surface; very little along the line 
of puncture. In four days the entire surface of the agar is covered with 
a whitish, smooth growth, and the agar at the top has changed to a 
faint yellowish green. Many crystals occur in the path of the needle. 
The agar is not liquefied or softened. 
Beef-Bouillon Cultures. —A slight clouding is noticeable in beef- 
bouillon (+15) cultures within 18 to 22 hours at room temperature 
(22 0 to 25 0 C.), increasing in density until a thick, viscid sediment forms 
in the bottom of the tube. When shaken, this sediment rises in a thick 
coherent, ropelike swirl. In bouillon cultures of three to five days* 
growth the solution becomes slightly greened, and a thin, whitish pellicle 
forms on the surface. This pellicle, which is composed of small masses 
of bacteria, is easily disturbed when shaken and falls in hundreds of 
tiny particles. In two weeks the medium has nearly cleared, a thick, 
whitish sediment has accumulated, and the solution is apple green in 
color, the fluorescence being most distinct toward the surface. In two 
months the medium has changed to a dark-amber color (Ridgway's 
“tawny”). Crystals may or may not occur. 
Neutral Beef Bouillon. —Growth occurs in 22 to 24 hours. There 
is a good growth in five days, and the medium has become a faint yel¬ 
lowish green color. 
