232 E. C. Andrews — Australian Flowering Plants. 



ment in Australia unless that, genus lias been modified to an 

 extent that it is scarcely recognizable as the world-wide type 

 until such time as it has flowered. 



Examples: The phyllodineous Acacias, Phyllanthus, and a 

 section of Cassia. And in such case the specialization of the 

 tonus has always taken place on the sandstone. This speciali- 

 zation it is which marks the Australian sandstone vegetation. 

 The primary types are to be found mainly as luxuriant forms 

 within the cosmopolitan tropics, whereas the secondary, special- 

 ized, xerophytic, and depauperate, types are to be found on the 

 sandy soils of extratropical Australia. This specialized vegeta- 

 tion has an origin relatively recent. 



The genera include Eucalyptus (300 sp.), Grevillea (200 

 sp.), Hakea (112-115 sp.), the phyllodineous Acacias (420 sp.), 

 Melaleuca (115 sp.), Goodenia (115 sp.), Candollea (105 

 sp.), Hibbertia (105 sp.), Persoonia (G5 sp.), BanJesia (50 

 sp.), Dryandra (50 sp.), Pultencea (100 sp.), Casuarina (25 

 sp.), and Ptilotus (76 sp.), and these originated on the sandy 

 soils of Australasia and have never travelled far from their 

 birthplace. 



This Australian vegetation belongs to families which origi- 

 nated partly in the north temperate regions, and, partly, in the 

 tropics. Under stress of circumstances the plants tended to 

 migrate south from the tropics. One branch moved south into 

 Australia and developed the secondary specialized forms enum- 

 erated in the preceding paragraph, another branch travelled to 

 South Africa, and there under similar climatic influences, and 

 upon similar sandstone areas, it developed a flora analogous to 

 that of the specialized Australian types. Another moved down 

 South America, but did not meet conditions similar to those of 

 Africa and Australia. Another branch w'hich had moved down 

 all the great land connections between the northern and south- 

 ern continents developed in the cool and moist regions of ISTew 

 Zealand, Southeast Australia and South America. This type 

 perished in Africa during the great climatic differentiation. 



