252 BACTERIAL ORIGIN OF GUMS OF ARABIN GROUP. 



7. Amides are the best nitrogenous nutrients; peptone is of 



little use. A trace of asparagine is sufficient. 



8. Salts may accelerate, depress, or prevent slime-formation. 

 Traces of alkaline citrate or succinate were most favourable. 



9. Sumach tannin assists the formation of slime upon artificial 

 agar media. Oak tannin hinders the formation, but the 

 retarding effect may be neutralised by the addition of 

 glycerine. 



10. The bacterium might be used to distinguish certain tannins. 



11. Tannin probably acts physically by making the agar medium 

 more contractile, so that the organisms are slowly supplied 

 with nutrients in solution. 



12. The optimum temperature is 17° C. 



1 3. The most suitable medium, as deduced from the experiments, 



serves as a diagnostic for other slime bacteria. 



14. Gum acacia has not a cellulose origin. 



15. In the host plant it is formed from the wandering sugars, 



levulose and maltose. 



16. Manuring with saline matter does not promise to be a remedy 



for the prevention of gum-flux in fruit trees. 



17. Peach trees that were inoculated with Bad. acacice (from 



Acacia hinervata) developed gum-flux. 



18. The exudate was a metarabin gum. 



19. The host plant can convert Bad. acacice into Bad. mdara- 



binum, proving what had been suspected, that the latter is 

 a variety of the former producing an insoluble gum. 

 30. This explains the uniformity of the gums from certain 

 species of trees. 



EXPLANATION OF PLATES XI. -XII. 



Colonies of the arabin group bacteria upon nutrient glucose-gelatine. 

 Plate xi. 

 Fig. 1. — Bact. acacice ( x 30). 

 Fig. 2. — The same organism twelve months afterwards { x 30). 



Plate xii. 

 Fig. 3. — Bact. metarabinum ( x 38). 

 Fig. 4. — Bact. pararahimim ( x 22). 



