38i 



from the latter tree. The gum precipitate also contained a similar manganese- 

 bearing compound, and the changes in colour which took place with the gum 

 when this was precipitated by alcohol, were even more pronounced than with 

 that obtained from Araucaria Cunninghamn, as, on drying, it became almost of 

 a jet-black colour. 



So far as we are aware, gum has not previously been found in the class 

 of resins exuded by the Dammara group, and to its presence may, perhaps, be 

 traced the reason why a portion of the constituents of some resins are found to be 

 insoluble in alcohol. The peculiarity of the freshly precipitated gum in changing 

 on drying the first time to a jet-black colour is, perhaps, analogous to the formation 

 of the black lacqi;er of the Japanese and Chinese, obtained from species of Rhus. 



Amthis robusta. showing flow of Oleo-resin. Queensland. 



This peculiarity of blackening with the gum precipitates of both Agathis robusta and 

 Araucaria Cvmninghamii, was distinctly traceable to the changing of the inorganic 

 constituents, of which manganese and iron were present in some quantity. Man- 

 ganese has been shown to be a constituent of the latex of Rhus, and the darkening 



