MORPHOLOGY OF GALL OEGANISMS FliOM. VARIOUS SOURCES. 127 



IMMUNITY. 



Our studies are still incomplete. As far as they have gone the}'' seem 

 to indicate that repeated inoculations produce a heightened resist- 

 ance to further inoculations v,dth organisms of the original or of a 

 lessened grade of virulence, but that more virulent strains will still 

 produce galls on such plants, although the initial growth is usually 

 slow. 



OBSERVED DIFFERENCES IN CROWN-GALL ORGANISMS FROM 



VARIOUS SOURCES. 



MORPHOLOGY AND BEHAVIOR TOWARD STAINS. 

 METHODS OF STUDY. 



The measurements were made from 2-day agar streaks inoculated 

 from agar streaks. The slime was diluted in sterile water and 

 spread thinl}^ on clean covers. These covers were then dried, 

 flamed slightly, and stained with gentian violet. They were washed 

 in water only, mounted in balsam, and examined at once. All 

 the measurements were made by the same person (the senior writer) 

 and represent the range of variation obsei^ved. All the rods were 

 straight or nearly so, with rounded ends. With one or two excep- 

 tions all stained freely and uniformly. The measurements were 

 made in the summer of 1910, using a Zeiss 2-mm. n. a. 1.3 oil-immer- 

 sion lens and an eyepiece micrometer in a No. 6 compensating 

 ocular, with a No. 12 compensating ocular for orientation and con- 

 firmation, using north light. One space of the Zeiss stage micrometer 

 (1 mm. in 100 Th.) exactly equaled 12 spaces on the eyepiece microm- 

 eter, making one space on the latter equal to 0.833/i (confirmation 

 of a determination by Miss Brown), but in making the measure- 

 ments the value was for convenience reckoned at 0.8/i. The mor- 

 phology did not vary greatly from culture to culture, as may be seen 

 from the measurements given. 



Similar young agar cultures were used for the demonstration of 

 flagella (Pitfield's stain in most cases). The flageila were stained by 

 Miss Katlierine Bryan, but the sHdes were also examined by the 

 senior writer. 



For the acid-fast (Erlich Weigert) stain and the Gram's stain 

 somewhat older agar cultures were used. 



Old cultures were examined for spore formation, i. e., agar streak 

 19 days. For the examinations unstained in sterile water the top of 

 the streak was used. It was then stained in carbol fuchsin 3 minutes 

 and reexamined. Transfers were then made to sterile peptone 

 water (3 mm. loop) from each tube and these were then at once 



