Australian Flowering Plants. 207 



It may not be out of place at this stage to mention that 

 there is at least a double expectation of types such as Euca- 

 lyptus, Hakea, Persoonia, and Banksia, in both South Africa 

 and Australia, on the assumptions made by various biologists, 

 firstly, that Eucalyptus forests and other growths now peculiarly 

 Australian, were common in Cretaceous and Tertiary time in 

 the north temperate regions, and that under the pressure of 

 more aggressive types they were driven to Australia, and 

 secondly on the assumption made by certain biologists that a 

 land bridge directly connected South Africa and Western 

 Australia. For, firstly, on the assumption that Eucalyptus 

 originated in the Holartic region, as so many mammalian 

 groups appear to have done, 23 it should have retreated towards 

 South Africa during the general expulsion from the north, of 

 types unfitted to survive such as HaJcea, Grevillea, Erica, and 

 Eucalyptus itself, much in the same way as we may imagine 

 the Restiacese, Proteacese, and Podalyriese (Papilionaceas), to 

 have done. Eucalyptus belongs to a tribe which contains 28 

 genera, with about 700 species, many of the genera being large 

 and aggressive (Eucalyptus 300 species, Malaleuca 112, 

 Ba?chea about 70). Another large tribe, namely the Chamse- 

 lauciese, is found growing side by side with the Eucalyptus 

 tribe. Both are practically endemic in Australia, with the 

 exception of a few specialized waifs in outlying islands. Were 

 the genera of these tribes to be very few in number and were 

 these rare genera in turn to be monotypic or oligotypic and 

 specialized or archaic, with huge gaps in the continuity of their 

 distribution, these assumptions of land bridges directly con- 

 necting Southwest Africa and Southwest Australia might pass 

 unchallenged, but when both the tribes and the genera are so 

 vigorous, so admirably adapted to the soils and climate of the 

 South African sand wastes, it is incredible that Myrtacese such 

 as these should not have made use of one of the assumed land 

 bridges constructed by biologists apparently for the special 

 benefit of the Proteacea? and Resticea?, whose greatest desire, 

 if one may adopt this teleological form of speech, would appear 

 to be to dwell side by side with the myrtle group in their strong- 

 hold, namely Australia. But neither the genus Eucalyptus, nor 

 any members whatever of the great and aggressive tribes Lep- 

 tospermese and Chama?lauciese, occur in South Africa ! When, 

 in addition, it is found that the fossil leaf determinations of 

 the northern hemisphere cannot bear the searchlight of im- 



23 W. D. Matthew, Climate and Evolution, Annals New York Acad. Sci- 

 ence, vol. xxiv, pp. 171-318, 1915. 



