248 BACTERIAL ORIGIN OF GUMS OF ARABIX GROUP, 



produced in the different branches, but as the gum upon both 

 trees had exuded at a place about two inches from the ground, 

 the experiment, so far as this question was concerned, was a 

 failure. The gum was protected with thin rubber tissue, but this 

 shortly perished, and the gum was washed away^ b}'- the rain. 



Several other trees near the exjDerimental ones showed no signs 

 of gum-flux, so that it may be accepted, as shown by this field 

 experiment, that Bad. acacice can produce gum-tlux of the 

 Rosacece as well as of the Acacice. It is interesting to note that 

 the gum in this case descended the stem, which would point to 

 the majority of the bacteria travelling in the descending current, 

 probably in the cellular tissue of the bark, the place in which 

 levulose and maltose, the sugars of translocation, would be found. 

 There is, of course, the possibility that the gum exuded low down 

 on the stem in both cases owing to wounds being there, and there 

 only, but as the branches had at an earlier time been freely pruned 

 below and above the site of infection this objection is scarcely 

 tenable. 



One year later the fork of the tree which had been infected 

 with Bad. metarahinum showed signs of gum in several places, 

 and an oval piece of gum measuring 2x1 cm. and 2 mm. thick 

 in the centre was removed. A portion was tested and found to 

 be metarabinum. 



The third tree that had been infected with Bad. metarahinum 

 only showed a considerable gum-flux at a place where a wire 

 chafed the stem. The gum was of the metarabin variety. It is 

 curious that the branch in one case and the tree in the other, 

 both of which had been infected with the metarabin bacterium, 

 produced this gum a year after inoculation, and that control trees 

 showed no sign of gum. 



In January, 1904, one of the check trees of the previous year 

 was infected with a culture of Bad. acacice which had been grow- 

 ing in the laboratory for over a year, and with which most of the 

 experiments concerning the nutrition of the organism had been 



* Metarabin gums swell enormously with water and fall off. 



