128 BACTERIAL OKIGIN OF GUMS OF ARABIN GliOUP, 



others were incubated at 30° for 1, 2, 3, 4 and o hours before 

 being poured into Petri-dishes. From all the plates colonies of 

 bacteria were readily obtained, and most of these were Bact. 

 acacias. The slime bacillus, Bact. persicce, n.sp., first isolated from 

 the peach, was also found, together with a few inert bacteria. 

 The latter could not be induced to produce gum, and must there- 

 fore be considered as being adventitious saproph^'tes. 



The gum-flux of the cedar is thus shown to be caused by Bact. 

 acacice^ the metarabin portion probabl}^ being contributed by the 

 slime bacillus of the peach, Bctci. r>ersic(e, n.sp. 



YII. — The Gum-flux of the Peach. 



When the fruit of the peach-tree is alFected with gum-flux, 

 drops of an almost transparent, colourless and gelatinous gum 

 exude from insect punctures or wounds upon the surface. Speci- 

 mens of peaches diseased in this manner w^ere received from Mr. 

 tf. W. Potts, Principal of the Hawkesbury Agricultural College. 

 Some of the peaches contained the gum under considerable 

 pressure, for upon cutting across the lower ends of the chambers 

 containing the stones, large globules of gelatinous gum immedi- 

 ately protruded. 



The microscopical examination of stained films of the gum 

 showed the presence of immense numbers of small badly staining 

 (and therefore probably dead) bacteria. In this respect, as well 

 as in the microscopical appearance, the gum from the peach fruit 

 was identical with gum from similarl}-- affected almonds. In con- 

 firmation of the deduction drawn from the microscopical 

 observations it was found that, although many portions of gum 

 and gum-saturated tissue were infected into gelatine and other 

 media, only a few colonies of bacteria were obtained. The few 

 colonies that developed from about a dozen plates were those of 

 Bac. levaniformans and another sporulating bacillus, Bact, jyersiccp, 

 n.sp., which will be described in a future paper. A few yeasts 

 were also obtained, but in view of the undoubted bacterial origin 

 of the gum, as shown at any rate by the microscopical appearance 



