10 president's address. 



During the past year the Maclea}' Bacteriologist has concluded 

 his research upon the bacterium responsible for the production 

 of the important vegetable gum, araliin, by investigating the 

 nutrition of the micro-organism. ?Ie found that the gum was 

 formed in the plant from the wandering sugars, levulose and 

 maltose, and that it could not have a cellulosic origin (the present 

 botanical theory) because the saccharine products of celluloses 

 are not only incapable of being a source of gum, but they actually 

 prevent its formation. Arabin, the essential constituent of Gum 

 Acacia, is readily soluble in water, while metarabin, the funda- 

 mental substance of Cherry-tree Gum, is insoluble. The gums 

 obtained from certain kinds of trees are very uniform in char- 

 acter, being one or other of these or else a remarkably constant 

 mixture. The reason of this was found to be that the tree has 

 the power of profoundly altering the physiological activity of the 

 gum-forming microbe, causing it to produce the soluble or the 

 insoluble variety. The research also showed the possibility of 

 the organism being used in the examination of tannins, some of 

 which assist, while others hinder, the formation of slime upon 

 artificial media. 



In continuation of the subject of the general production of 

 vegetable gums by microbes. Dr. Greig Smith investigated the 

 gum-flux of Jlaci'ozamia spiralis and found that it was caused by 

 a new organism. 



The Sugar-Cane sometimes exhibits, when cut longitudinally, 

 brilliantly coloured red vascular strings, and microscopical obser- 

 vation shows that the colour is due to the large vessels being 

 filled with a red slime or gum. Many bacteria may produce 

 gum, but the colour is imparted to it by a particular microscopic 

 mould which, when in the cane, can only produce the colour 

 when growing in gum. The most suitable gum appeared to be. 

 a white galactan, the product of Bac. pseiidarabiniis. A race of 

 the same micro-organism producing a yellow slime was isolated 

 from the Quince. 



Of considerable interest is the constancy or variation of the 

 slime-products of bacteria, which are recognised chiefly by the 



