Vlll 



photographer and printer, the cutting out of anatomical details by the colour 

 screens has been quite obviated ; whilst the colours aid in differentiating the various 

 tissues and structures — the cell walls in the most minute cases being well defined. 



The genus Callitris has been dealt with somewhat more full\- than the 

 others, for the reason that, next to Eucalyptus, of the Myrtaceous Order, it is 

 probably the most important in Australia, having a more extensive geographical 

 distribution than any other genus of Australian Conifers. It has thus been 

 possible to obtain more comprehensi\'e material from its se^•eral species, and so 

 have been exploited nearly all the known species of Callitris growing in Australia 

 and Tasmania, whilst material of some of them has been procured from remote 

 localities, and has been collected at various times of the year. By working in so 

 extensive a field it has been possible to determine the correlation of the several 

 species, to rearrange their scientific sequence, and to far more widely extend 

 their economic possibilities. 



Other important genera, such as Araucaria, Agathis, Dacrydiiim, Phyllo- 

 cladiis and Podocarpus, have also been extensively treated. 



Although it has been possible to show a probable evolution in the species 

 of Callitris, yet, as regards the sequence of the several genera, it was found not 

 so easy, in \aew of the absence of a number from this continent ; but we have 

 little doubt that when the whole of the genera belonging to the Coniferje shall 

 have been investigated on similar lines, a table of origin for the whole family will 

 be evolved. 



We have endeavoured, so far as the material and time would allow, to 

 point out the several stages through which a genus has developed, to locate distinct 

 botanical and chemical characteristics, and to determine those peculiar to, and 

 distinctive of, any particular species. 



By such a method as here adopted it may eventually be possible, with 

 extended investigation, to chscover the laws governing the formation of species, 

 to indicate their evolutionary processes, and thus to locate their correct place in 

 nature. 



We are not insensible of some imperfections in this work, but it is felt that 

 the time has arrived when the results so far obtained should be published. The 

 doubtful points awaiting solution are many, and too diverse for us to hope to 

 solve them during our short lives. 



That we might add some new scientific facts to the world's knowledge, 



and assist in the development of the natural resources of Australia has been the 



incentive throughout this work . 



R.T.B. 



H.G.S. 

 Technological Museum, Sydney. 



June, igio. 



