WILT-DISEASES OF TOBACCO. 241 



Pcritrichiate flagella: There are 4 to 8, which are 3 to 4 times the length of the rod. 



Endos pores: These are formed after a month in both fluid and solid media. They are found very 

 often in the top of agar-streak cultures grown for 3 months at room temperatures, but not in the 

 lower part of the streak. They are not described or figured. 



Early pellicle: This appears the third day on neutral peptonized beef-bouillon with subsequent 

 brown stain of the fluid; the pellicle breaks upon shaking into parti-colored portions, blue and white. 

 The pellicle becomes gray and rather granular, and after a month there is a black ring. 



Liquefaction of gelatin: In stab-cultures liquefaction begins to appear the second day. After 4 

 days there is a distinct funnel-form liquefaction. After about 3 weeks all of the gelatin is liquefied, 

 and gradually stained gray-black. In streak cultures all of the gelatin is liquefied in 2 weeks. This 

 contradicts an earlier statement by Uyeda. 



Color and rapidity of growth on agar-plates: The colonies appear within 24 hours at August tem- 

 peratures. They assume a reddish color after about a week and then gradually change to a dirty gray 

 and black. Frequently giant colonies appear on the plate cultures and these become ringed concen- 

 trically. Rhomboidal crystals of ammonium magnesium phosphate are frequent in the agar. 



Disorganization of potato slices: This takes place within one or two weeks. The growth is yellow. 



Coagulation of milk by the formation of an acid: Milk inoculated with this organism becomes 

 strongly acid and is coagulated. This contradicts an earlier statement. Later it is partially pep- 

 tonized and becomes chocolate -brown and feebly alkaline. 



Thermal death-point: This is 54 C. At 53 the result was not uniform. In one place 55 is 

 stated to be the "maximum" temperature. 



Anaerobism: In sugar-agar it grew well in the depths of the stab. In bouillon in fermentation- 

 tubes it clouded the closed end. It also grew very well in an atmosphere of hydrogen. 



Acids: Acids were developed in various saccharine media. 



Gas: Scanty development of gas in glucose-agar and glucose-bouillon. Kind of gas not stated. 



Indol: A weak indol-reaction was detected in young cultures. 



Stains by Gram. Reduces litmus in milk. 



Non-infectious to egg-plant and tomato. 



Other characteristics of the organism are as follows : It is a short rod with rounded ends 

 usually i to 1.2 by 0.5 to 0.7^ (fig. 129). In the plant it occurs often isolated, but some- 

 times in pairs. In cultures it is single, in pairs, or fours. Even in cultures 2 to 3 weeks 

 old it rarely forms chains. It varies somewhat in size according to conditions of growth, 

 e. g., in bouillon the rods are somewhat larger than on agar. Capsules occur in old agar 

 cultures. 



On gelatin-plates, in i to 2 days, small colonies appear both on the surface and in the 

 depths. Magnified 50 times the surface colonies are roundish with an irregular edge, some- 

 what granular and darkest in the center. After 4 or 5 days the gelatin around such colonies 

 is liquefied centrifugally and there is a bacterial sediment in the fluid. After 6 days the 

 colony is somewhat beaker-form. After a week the colonies retain their original form, 

 floating in the liquefied gelatin. The buried colonies are ellipsoidal and within a few days 

 they fuse into a very small mass. 



In agar-plates (fig. 130) the surface colonies are not granular, but very smooth, moist 

 and bright in their center. A membrane is often formed over the giant colonies. Rarely 

 the concentric giant colonies have a serrate margin. At first the surface colonies are white. 

 The buried colonies are elliptical or egg-shaped. They have a high sheen by transmitted 

 light; by reflected light they are bluish white and somewhat fluorescent. 



Growth on steamed potato at July temperatures is rapid, forming after a time a greenish- 

 yellow layer. In course of i to 2 weeks the substratum becomes gray-black. This pigment 

 is soluble in water and is due to tyrosinase, an oxydizing enzyme. The black pigment from 

 agar-streak-cultures is readily soluble in water, very little in alcohol or glycerin, and not at 

 all in benzine, ether, or chloroform. This pigment is produced within a few days in agar, 

 bouillon, gelatin, potato, and milk. In August, at 30 C. (room-temperature), the pro- 

 duction of pigment was very rapid. Bouillon and milk are wholly blackened at a high 

 temperature (35 C.) and a black ring is often formed on the wall of the tube at the surface 

 of the fluid. 



