INTRODUCTION. 



THE issue of this Atlas has been for a long time under contemplation. Indeed material 

 for it accumulated here since 1847, when the author commenced also in reference 

 to the Eucalypts his local Australian studies, ever since carried on as opportunities 

 occurred. But the subject is so large and surrounded by so many perplexities, that 

 even now he can offer his observations only fragmentary. It is acknowledged, that 

 of all generic groups of Australian plants that of Eucalyptus is the most difficult 

 for elaboration. This arises not only from the very large number of species, Euca- 

 lyptus being in this respect solely surpassed by Acacia, but also because the habitual 

 resemblance of many specific forms is very deceptive ; again, because fruits and 

 especially flowers of these trees are not within easy reach of travelling collectors at 

 all seasons ; also further, in consequence of several species differing in regard to the 

 persistence or secession of their bark according to geologic influences ; and lastly, 

 because the species are distributed over the whole Australian continent and Tasmania, 

 some even extending to the Indian islands, though none occurring in New Zealand. 

 Yet to assign to each species its proper systematic place involves the study of all 

 allied congeners, and these are often not to be found in natural proximity, but only 

 dispersed at wide distances in Australia. Great obstacles arose also in identifying the 

 earlier discovered species, their first description being generally of extreme briefness 

 and imperfection, so much so that it was only in a few of the pinncipal Museum- 

 collections of Europe, where from comparison of autographically named original 

 specimens many of our Eucalypts could be unmistakably recognized. Still already 

 in 1855 and 1856, during Aug. Gregory's expedition, the author endeavoured to shed 

 fuller light on the tropical Eucalypts by close observations instituted in their natural 

 haunts, the results being rendered known in the journal of proceedings of the Liunean 

 Society in 1858, p. 81-101. Similar and still ampler notes were extended connectedly 

 to the extra-tropical species, both eastern and western, in 1860 (Fragm. Phytogr. 

 Austr. ii., 32-71). In these writings many of the characteristics, on which dependence 

 can be placed for specific discrimination in this singular genus, were first drawn into 



