386 BACTERIAL ORIGIN OF GUMS OF ARABIN GROUP, 



saccharose and reducing sugars, and was used for the test-tube 

 reactions. Flocculent white precipitates were obtained with 

 basic and ainmoniacal lead acetates. Neutral lead acetate gave 

 no reaction. Neither did the salts of silver and mercury. The 

 hydrates of calcium and barium gave no precipitate. Copper 

 sulphate followed by potassium hydrate gave a flocculent pre- 

 cipitate which became cohesive on boiling and did not darken in 

 colour. When tested at a later date by the method recommended 

 by Maben,* borax stiffened the mucilage, while basic lead acetate 

 and also ferric chloride hardened the gum acids forming cohesive 

 masses. Tannic acid had no effect beyond producing an 

 opalescence. 



The natural gum of Acacia pe^minervis is not entirely soluble 

 in water; the major portion simply swells up to form gelatinous 

 lumps, t The portion that does dissolve acts towards the salts of 



* Maben, Pharm. Jour. [3] xx., 719. 

 t ''Acacia penniiierviA, Sieb., ' B. Fl.' ii., 362. 

 A " blackwood " and " mountain hickory." Found in Tasmania, Victoria, 

 New South Wales and Queensland. Sample from Quiedong, near Bombala, 

 New South Wales. 



Arabin 70*3 



Metarabin 11 "42 



Moisture 1 6 "67 



Ash 0-66 



While not approaching the best kinds of gum arabic in lightness of colour, 

 it is the palest and cleanest looking of the coast Wattle gums described in 

 this paper. Colour pale sherry to orange. It has a bright fracture, although 

 a sample received from Brown's Camp, Delegate, and obtained from tarious 

 trees 6 feet 2 inches, 6 feet in diameter and 40 feet to 60 feet high, has a 

 dull fracture like A. binervata. It is interesting to note that in the Quiedong 

 district the gum was obtained in abundance from shrubs or small trees 

 growing in low ground, while in the Braidwood district no gum whatever 

 could be found on trees of this species, where it grows at high elevations, and 

 at Delegate, at moderately great elevations, only very small quantities of 

 gum could be obtained. The inference is that this species yields gum plenti- 

 fully from shrubs at low elevations, but little or none from trees at high 

 ones. The same thing has been found to hold good to some extent in regard 

 to A. dealhata. These observations point to the truth of the oft-expressed 

 surmise that gum is a pathological product or the product of plants in uncon. 

 genial surroundings. ' — Maiden, Pharm. -Jour. [3] xx. (1890), 980-1. 



