132 
Journal of Agricultural Research 
Vol. XXI, No. 2 
media as expressed in Fuller's scale was adjusted by titration with 
phenolphthalein as an indicator, in which the first appearance of a 
permanent pink color was taken as the neutral point. Color determina¬ 
tions were made by reference to Ridgway’s color standards. 1 Inocula¬ 
tions were made from a water suspension of the organism. A culture 
of Bacillus coli was carried in a parallel series of tests on practically all 
the media. 
Agar poured peates. —On + io beef-peptone agar colonies appeared 
in 24 hours. In 48 hours surface colonies were 1 mm. in diameter, trans¬ 
lucent, and slightly fluorescent. In 5 days surface colonies were 2 
to 3 mm. in diameter, circular with entire margins, convex or pulvinate, 
smooth, glistening, translucent, and straw yellow. Submerged colonies 
remained very small and were lenticular in shape, except that those in 
contact with the bottom of the dish spread underneath the agar to form 
circular, grayish fluorescent spots. The agar was unchanged in color, 
and there was no odor. 
On plain potato agar, growth was more abundant and the yellow 
pigment was more pronounced. In 10 days colonies were 8 mm. in 
diameter, circular with entire margins, pulvinate, smooth, glistening, 
and naphthalene yellow (PI. 28, D). Submerged colonies remained 
small and lenticular or three-cornered. On potato agar with 2 per cent 
peptone the colonies attained a diameter of 7 mm. in 5 days. On+5 
potato soft agar (1 % per cent), colonies resulting from the planting of a 
2-mm. loop of a water suspension on the agar surface attained a diameter 
of 40 mm. in 7 days. In the peripheral zone there were distinct radial 
striations of denser pigmentation, while the central zone showed a gran¬ 
ular or netted pattern. The consistency was butyrous or gelatinous. 
Agar stabs. —On +10 beef-peptone agar, a rather scanty Aliform 
growth with a beaded outline occurred along the stab, more noticeably 
toward the top; and the surface growth, which was rather scanty at the 
end of 2 days, later became abundant. 
On plain potato agar, scanty growth occurred along the upper 5 to 10 
mm. during the Arst 2 days and later was visible along the upper 15 111111., 
but not at the lower end of the stab. The surface growth in 2 days was 
abundant, convex, smooth, glistening, and naphthalene yellow. After 
18 days the entire surface was covered 5 mm. deep. 
Agar seant.— On + 10 beef-pep tone agar, the growth was abundant, 
at Arst Aliform, later spreading with an entire margin, raised, smooth, 
glistening, tianslucent, at 2 days massicot yellow, at 5 days mustard 
yellow, and at 19 days anilin yellow. Along the edge of the culture 
there were short parallel striations of denser color perpendicular to the 
margin. The agar remained unchanged in color, and there was no odor. 
On plain potato agar the growth was more vigorous and in 5 days was 
‘ Ridgeway. Robert. color standards and color nomenclature. 43 p., 53 col. pi. Washington 
D. C., igia. 
