5-42 BACTERIAL ORIGIN OF GUMS OF AKABIN GROUP, 



.Specimens of the fruit, etc., of Sterculia diversifolia, showing 

 numerous gum-drops upon the seed-capsules and twigs, were sent 

 to me by ^Ir. H. W. Potts, Principal of the Hawkesbury Agri- 

 cultural College. The substance of the capsules was saturated 

 with a mucilage which oozed through insect punctures in the 

 pods, and formed gum-drops upon the outside as it dried. From 

 these specimens I hoped to obtain an organism capable of forming 

 pararabin. 



Bacteria were readily obtained, in the manner that I have 

 previously described, from portions of the punctured fruits, from 

 the very young entire fruits (measuring about 1 cm. in length) 

 and from unpunctured twigs. 



The colonies were those of Bad. acacice, and of races of another 

 bacterium which was closely investigated. Since the bacteria 

 were obtained from the twigs and unpunctured young pods, it is 

 clear that the plant had not been infected by the same insects 

 that made the holes through which the gum exuded. Infection 

 must have occurred at another place, possibly on the stem, and 

 at a less recent date. 



When infected upon the surfaces of plates of saccharose-potato- 

 agar, the unknown bacterium grew as a whitish slime which could 

 be readily removed. A watery suspension of the slime was 

 coagulated by copper sulphate (1% and 10%), ferric chloride, 

 aluminium hydrate, lead acetate (10%), basic lead acetate, baryta 

 water, milk of lime, and silver nitrate (5%). Upon standing a 

 sediment separated out from the slime, and the almost clear 

 supernatant liquid also gave precipitates with the reagents 

 enumerated. 



When the specimens of fruit arrived at the laboratory, several 

 pods were soaked in water, and the mucilage which exuded was 

 precipitated with alcohol. But a small precipitate was obtained 

 from a fairly mucilaginous solution, and when this small quantity 

 was dissolved or diffused in water it was precipitated by lead 

 acetate, baryta water, copper sulphate, silver nitrate, and slightly 

 with ferric chloride. These reactions were sufficient to show 

 that the Sterculia mucilai>;e and the bacterial slime have certain 



