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[ CHEMISTRY OF THE EXUDATION. 



This exudation, which consisted almost entirely of gum, was obtained 

 from a large cultivated tree, 2 feet in diameter, growing at Marrickville, near 

 Sydney, and was collected during the last three months of the year 1908. Sex 

 appears to have no influence upon the composition of the exudation ; because, 

 when the large green fruits were cut through, they were found to be charged 

 with sap identical in appearance and composition with that obtained from the 

 trunk of the tree. When dried, this gum from the fruits had the same slightly 

 aromatic odour, was quite as brittle, dissolved just as readily in water to a turbid 

 solution, due to the presence of the same small amount of oleo-resin, and formed 

 the same insoluble jelly when agitated with ether. 



Dr. Lauterer (loc. cit.) says that the percentage amount of gum and resin 

 in the exudation of this tree varies much at different times of the year, but 

 our results do not confirm that statement. The material obtained from our 

 specimen was identical in composition, whether obtained in September or in 

 December, and a specimen of the gum of A. Bidwilli in our possession, which 

 was collected in Brisbane in July, the colder time of the year, was found to 

 be identical in composition with that of our own collecting. It had the same 

 slightly aromatic odour, and an analysis showed it to contain less than 2 per cent. 

 of oleo-resin. The gum was also readily soluble in cold water, just as adhesive, 

 and on agitating with ether it eventually changed largely into the jelly-like 

 insoluble form, only this change took place less readily than with the freshly 

 procured material. The tree growing near Sydney was wounded, September, igo8, 

 by cutting quite through the bark in places, and also by cutting off the old scars 

 left by the decayed branches. A very fluid liquid quickly exuded from the 

 wounds, and formed tears which soon dried, becoming quite hard and brittle. 

 In the places where the bark had been cut through, the upward flow continued 

 for months ; this has been referred to previously under A . Cunninghamii. The 

 exudation when dried resembled in appearance some kinds of wattle gum. It 

 was amber-coloured, mostly semi-transparent, very brittle, bright in the fracture, 

 and was slightly aromatic. This gum-like substance dissolved somewhat 

 readily in water to a turbid, slightly acid solution, which gave a dense pre- 

 cipitate on the addition of excess of alcohol. The precipitate, when spread on 

 glass, became quite a transparent gum which again dissolved readily in water. It 

 did not become dark coloured on drying like the gum of A . Ctmninghamii , although 

 manganese was detected in it. There were present in the exudation very small 

 amounts of volatile oil and resin, thus differing from that of A . Cunninghamii, and 

 also from the exudations of the Coniferse generally. Four grams of picked gum, 

 dissolved in water, and agitated with 25 c.c. of ether, soon separated the gum 

 as an insoluble jelly, and from which the ether had removed most of the resin, 



2 A 



