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XV. TIMBERS. 



(fl) Macroscopic AL. 



In regard to colour, the timbers may be divided into two classes, viz., those 

 having a pale or white heartwood, and those with a coloured duramen. 



The latter class is quite limited in its number of species, including as it 

 does only two, \iz. : — 



C. intratropica. 

 C. aroiosa. 



While the former includes : — 



C. glauca. 



C. calcarata. 



C. Macleayana. 



C. rhomboidea. 



C. gracilis. 



C. Tasmanica. 



C. verrucosa. 



C. Muelleri. 



Too much reliance, however, must not, in this connection, be placed on 

 colour, as it varies in depth in the same species, and is then largely due to the 

 presence of an excess of chemical bodies peculiar to these timbers. 



As a systematic classification this feature is of little use, for dark and light 

 coloured timbers may be found in trees of the same species, and specimens 

 illustrating this feature are exhibited in this Museum. 



The lighter shade of timber hardly resembles in character that of the Pi nil s 

 of commerce, being a closer-grained and harder wood, whilst the darker-coloured 

 varieties are still heavier and more ornamental ; both characters are dealt with 

 more fully under the respective species. 



(b) Microscopical. 



A microscopical examination of the permanent or secondary tissue of these 

 Conifers shows it to consist almost entirely of prosenchymatous cells or typical 

 sclerenchymatous tissue, but parenchymatous tissue is found scattered throughout 

 the tracheids in the rays, the right-angled end walls being seen in the sections of 

 these medullary rays, with their uniform cell structure. Pitted cells in single rows 

 in the radial walls form a characteristic feature; of all the lra( licids. 



The disposition of the jjittcd cells present no variation Ikhii those of non- 

 Australian Conifers, or other plants having this characteristic cell-wall structure ; 



