BY U. GREIG SMITH. 125 



constituent of the gum. The gum levan which it produces from 

 saccharose is readily h3^drolysed in acid fluids, and would bo 

 hydrolysed by the acid juices of the plant as soon as it was 

 formed. For this reason the presence of the organism may be 

 looked upon as accidental. The secretion of invertase by this 

 bacillus, however, must not be forgotten, and possibly the inver- 

 tase may assist the other bacteria to form the gum. 



The races of Bad. acacur. and Bact. metarabhium were identical 

 with those already described. Quantities of the gum were pre- 

 pared by growing the bacteria upon saccharose-potato-tannin agar 

 and subsequentl}'- obtaining the gum from the slime.* From the 

 characters of the gum-acids as regards solubility and the forma- 

 tion of arabinose and galactose on hydrolysis, there was no doubt 

 of the identity of the bacteria. 



Summary. — The investigation showed that the gum-flux of the 

 vine is caused by Bact. acacice and Bad. metarabinum. 



V. — The Gum-flux of the Plum. 



Among the Rosacea? the plum frequently exudes gum from 

 punctures and wounds on the stem and branches, and, like the 

 gum from the other members of the family, plum gum is recog- 

 nised as belonging to the arabin group. 



I received specimens of wood and bark with adhering tears and 

 globules of a pale straw to reddish-coloured gum from Mr. Cheel, 

 who had obtained the specimens from the Crawford River 

 district, about six miles from Bullahdelah. Unfortunately, the 

 specimens as I received them were rather dr}^ a fortnight having 

 elapsed since they had been removed from the tree. The gum 

 masses, however, were large, and while the outer layers were 



* The potato-extract used in the preparation of the agar was originally 

 made by adding an equal volume of water to the juice of old potatoes. With 

 new or early potatoes the juice may require to be much diluted. With certain 

 potatoes I obtained the best results by adding 1 part of juice to 9 parts of 

 water. This, however, will be discussed in a future paper upon the nutrition 

 of the bacteria. 



