37 



shorter. Flagella-beariiig rods of the former are shown in Plate I, fig. 

 10, and of the latter in Plate I, fig. 11. 



Rods were frequently seen in process of division, and occasionally 

 two pairs were found joined end to end. Chains were never seen in 

 the host plant or in young cultures. Even in old cultures in beef 

 broth (rim excluded) and on potato and standard nutrient agar free 

 from sugar, they were very rare. Prolonged search would, however, 

 sometimes be rewarded by the discovery of a chain of 6 to 12 seg- 

 ments. As in case of Ps. campestris the tendency to form chains in 

 the ordinar}' culture media is very slight. In sugar agar, on the con- 

 trary, and also on banaiia, sweet potato, etc., chains and long rods 

 are ver}'^ common. These are usuallj^ mixed in with zoogloete and 

 the short elements. In such media the short elements often grow 

 out into undivided filaments 50 to 150 a< iu length. In many of these 

 1 was unable to discover even a trace of septa. In others the seg- 

 ments were distinct. Transferred to alkaline beef broth or common 

 agar the long rods and chains disappear and the ordinary form 

 abounds. This growth in the form of chains and filaments was 

 observed repeatedly in cultures abounding in sugar; in fact, it may 

 be produced at will by inoculating this organism into agar rich in 

 grape or cane sugar. Two of these long rods taken from a 30 per 

 cent cane sugar agar are shown in Plate I, fig. 8c. Ps. campestris and 

 Ps. phaseoU behave in the same way ;n the presence of an excess of 

 sugar. 



No branched forms have ever been seen. Like Ps. campestris some 

 of the rods appear to be slightly curved, but the chains are not 

 crooked or twisted, as in case of vibrios. 



MOTILITY. 



The organism is motile, at least in early stages of its growth, in a 

 variety of media. These movements, which are tumbling and dart- 

 ing, are accomplished by means of one long polar flagellum. This 

 flagellum was stained only after repeated trials. It must be very 

 effectually mordanted. I finally succeeded with Van Ermengem's 

 nitrate of silver method, with Fischer's stain, and with Dr. V. A. 

 Mooi-e's modification of Loeflfiei-'s stain. As a rule tlie flagella were 

 only feebly stained. The ai)pearance of this organ is shown in Plate I, 

 fig. l». Figures of the flagella of Ps. campestris and Ps. pliaseoli are 

 introduced for comparison. In some cases it seems as if the flagellum 

 were given off slightly below the end of the rod, both in this species 

 and in Ps. campestris, but of this I could not be entirely certain. 

 Motility was observed in potato cultures -2 to 4 weeks old, but I was 

 never able to see any in rods taken dii-ectly from the closely packed 

 yellow masses inside the bundles of diseased bulbs. This material 

 was examined very carefully in distilled water. 



