544 DKVKLOPMENT OF THE N.O. MYRTACEjE % 



(d)The practical isolation of Australia from the rest of the tem- 

 perate and tropical world during the latest Cretaceous and a great 

 portion of the Tertiary. 



(c)The morphological characters common to the majority of the 

 Myrtacese. 



The present distribution of the family has already been con- 

 sidered, and may be stated very briefly in this connection. 



The greatest number of species by far occur in tropical and sub- 

 tropical America, while Australia is the area of greatest density 

 after America. The family is practically absent in the cold tem- 

 perate regions of both hemispheres. The fleshy-fruited genera are 

 uncommon in Australia, but are extremely common in the tropics 

 of both hemispheres. The capsular-fruited genera rarely get 

 beyond the Australasian Region or the Indian Archipelago. The 

 Chamaslaucieae are confined to Australia, especially to the Western 

 half of the Continent. 



The present environment of the Myrtaceae is peculiar, one group, 

 namely, the fleshy-fruited genera, characterised by abundant shel- 

 ter, moisture and warmth; another group, namely, the Metro- 

 sidereae, selecting situations of shelter, moisture and warmth, but 

 not being so absolutely dependent on these factors acting in con- 

 junction, as the Myrteae; another group, namely, the Leptosper- 

 meae, exclusive of Metrosidereae, shows an ability to flourish in an 

 excessively sandy and porous soil, and under moist or dry, hot or 

 moderately cold conditions, while the Chamaelaucieae, and certain 

 genera of the Leptospermeae, such as the Baeckeaeae, appear to 

 flourish both in poor sandy soil and in dry situations. 



The geography of the Cretaceous appears to have been one of 

 lowlying plains, mild, genial and moist climate of almost cosmo- 

 politan range. The soil of Australia, at that period, appears to 

 have been very sandy and porous, taken as a whole. 



High mountains, great deserts, glaciated polar regions and large 

 continents characterise modern geographies, whereas, in the closing 

 Mesozoic, the inland seas were large, the land-relief slight, and the 

 climate genial and moist. 



