82 



We have shown in the articles deaUng with the freshly exuded oleo-resins 

 of both AriiKcariii Ciiniiiiig/uiniii, and AgafJiis robiisfa, that a manganese compoinid 

 was associated with these exudations, that it was precipitated by alcohol, together 

 with the gum, and that wht-'u tlius siixuated from the other constituents of the 

 exudations, it became dark coloured on drying; with Agathis it was quite black; 

 also that this blackening appears to be due to the alteration of the manganese 

 under the inlluence of the ox\-gen in the air. The appearance of this dark-coloured 



gum under the microscope 

 strongly resembled the 

 dark material in the cells 

 of the timber, especially in 

 their lighter portions. The 

 manganese reactions were 

 obtained with the ash of all 

 the species of Callitris tim- 

 ber tested, although in 

 some instances the green 

 colour with the alkali test 

 w^as very faint, and this 

 was always the case with 

 the ash of the lighter- 

 coloured timbers. Those 

 specimens of C. calcarata 

 which were tested, usually 

 gave a faint reaction, and 

 the timber was mostly light 

 coloured, although a recent 

 specimen from Wellington, Xew South Wales, which in the centre of the tree was 

 a little darker in colour, gave a more definite manganese reaction. The timber of 

 C glauca is usualK' of a darker colour than is that of C. calcarata, and conse- 

 quently it gave the reactions for manganese far more strongly. The ash of the 

 bark of C. glauca, too, also gave a marked reaction for manganese, while that of 

 the bark of C. calcarata was less marked. 



Callitris calcarata is a species which usually grows on the hilly portion of 

 the countrv, while C. glauca is mostly found growing on the fiats and level country. 



The timber of C. intratropica was quite dark coloured, and consequently 

 the reaction for manganese in the ash was most distinct, the ])ercentagc being 

 somewhat high. The timber of C. verrucosa was light coloured, and the green 

 colour reaction for manganese difficult to obtain, it being necessary to increase 

 the amount of ash used to twice the ordinar\- amouiil. Tlic limber of Actiim- 

 strohus, although small, was comparatively dark coloured in places, and tliis ])()rti(in 



■"iri-\ -Ti'j i'jLtion oi um 



Thi- d.irk liii'"^ are \\\<- nu'dullary 

 ray*, with their manfiancst* compound contents and the rectangular 

 dark markings a similar substance- in tiic tracheids. C glauca^ 

 X 80. 



