8o 



XXI, OCCURREXCE OF A MAXGAXESE COMPOUXD IX THE 

 AUSTRAL! AX COXIFER.E. 



In the anatomical investigations of the timber, bark, and leaves of the 

 various species, there was found to be present, in a more or less degree, a naturally 

 brownish-bronze coloured substance, which invariably stained dark brown or 

 almost black with haematoxylin. 



It is found to occur in the wood, bark, and leaves of CaUitris and Actinostrobus. 



It is not by anv means equally distributed in the wood tissues of the various 

 species, being most plentiful in C. intratropica, and least abundant in C. Muelleri; 



its presence appears to give 



the relatively dark and light 

 colour of the timber of the 

 respective species, this being 

 the only method of detect- 

 ing its presence macrosco- 

 picaUy. 



Microscopicalh' it forms 

 a conspicuous feature in all 

 the timber sections, for it 

 occurs in the lumina of the 

 tracheids, the lamella and 

 septa formed at the junction 

 of the tracheidal walls and 

 the parenchymatous cells 

 of the rays, both inner and 

 outer cells, and sometimes 

 the pith cells. 



The darker colour of the 

 wood is, therefore, largely 

 due to the presence of this substance in all these parts in a more or less degree. 



Amongst bark cells it is confined mostly to the outer cortex, and is 

 strongly marked in almost all the sections given, and often in the secretory cells of 

 the oleo-resin cavities, and is thus a conspicuous object in bark sections. 



In the leaves it occurs in the cells of the parenchymatous vessels clustered 

 below the decurrent channel, often in those enclosing the phloem of the branchlet, 

 and in some of the cross sections of the branchlet and decurrent leaves it is seen 

 to fill the pith cells, the radial cells from these, and also those connecting with them. 



In Athrotaxis, Araucaria, Agathis, Phyllocladus, and Podocat'pus it occurs 

 111 iiK' timber, and in the last in the least amount. 



S'Clion through a branchlet and decurrent leaves, showing the dark 

 brown substance or manganese compound in thu cells surrounding 

 the median axis. C. robusta, x 80. (See also coloured plate, 



Fi^'ir- 44.) 



