322 BACTERIA IN RELATION TO PLANT DISEASES. 
In gelatin-stab-cultures liquefaction begins at the surface and passes to the walls of the 
tube and thence horizontally downward more and more slowly, the depths of the gelatin, 
even along the track of the needle, remaining solid for a long time (fig. 129). The liquefied 
gelatin may be cloudy at first as in the middle tube but is finally clear unless shaken. The 
writer observed some differences in the rate of liquefaction, these depending on the kind 
of gelatin medium used. Occasionally in unfavorable gelatins there was no liquefaction. 
On peptonized beef-broth-gelatin feebly acid to litmus, growth was feeble. In the same 
gelatin rendered more alkaline (feebly alkaline to litmus) growth was better. In stab- 
cultures in the latter, liquefaction began in 24 hours and was completed (10 cc.) in 15 days 
at 17° to19° C. A much longer time than this is often required for complete liquefaction— 
two months or more. In the writer’s experiments o gelatin was liquefied more rapidly 
than +20 or —20 gelatin. According to Harding liquefaction begins in 3 to 18 days. 
In streak-cultures on Loeffler’s blood-serum at the end of 20 days at about 23° C. there 
was an abundant dull yellow growth, and a slow liquefaction. All the upper part of the 
slant was fluid or transparent. Only the extreme base of the serum under the V had retained 
its original opaque-white color. The fluid serum was pale brownish by reflected light, and 
the stain and transparency passed down into the solid part. In comparison with a streak 
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Fig. 125.* Fig. 126.7 Fig. 127.t 
of Bact. phaseoli of the same age Bact. campestre showed more liquefaction and stain, but 
not more growth: By reflected light the contrast in color of the serum, white vs. brownish, 
was decided (tests of May, 1909). Subsequently this contrast became less. 
It is an organism rather sensitive to acids, even those derived from plants. Complete 
data (quantitive) are not available. Further experiments should be made. According to 
Harding the vitality of the organism is lessened by long cultivation, 7. ¢., it liquefies gelatin 
more slowly and is less resistant to heat and to desiccation. It destroys the middle lamella 
of cell-walls and possibly(?) on prolonged action the cellulose of crucifers, but not lignified 
tissues. It has no solvent action on Swedish filter-paper. It produces indol slowly in 
sugar-free peptonized beef-bouillon or peptonized Uschinsky’s solution; it does not reduce 
potassium nitrate to nitrite when grown in peptonized bouillon or with cane-sugar in 
Fischer’s solution. The organism had no characteristic odor, except (Harding) the strong 
odor of crucifers when grown on these substrata and in bouillon an odor of sweet corn. 
*Fic. 125.—Bacterium campestre from a potato culture kept 4 months in ice-box at 12° C. Fluid at bottom of 
culture was filled solid with bacteria, but the growth was still a fresh yellow color. Drawn unstained from a hanging 
drop with 2 mm. objective, 1.30 n. a., and 12 compensating ocular, Mar. 8, 1905. 
{Fic. 126.—Bacterium campestre, drawn unstained from a hanging drop Mar. 9, 1905, after 48 hours in beef 
bouillon at 30°C. The organism was actively motile and short; termo-like paired rods were the common form. No 
long rods were observed. Bouillon was thinly clouded. It was made from a typical culture on potato, i.e., that which 
furnished material for fig. 125. +" 
tFic. 127.—Bacterium campestre, from a very old potato culture (brownish yellow slime stirred up in water) 
made Mar. 8, 1905, from a culture inoculated Oct. 4, 1904, and kept in a refrigerator a long time at 12°C. A larger 
proportion of the rods were vacuolate than are here shown, 
a 
