467 



(3) Difficulty is experienced at times in attempting to 

 separate certain allied species of eucalypts and acacias 

 which may exist in neighbouring regions separated by a 

 natural barrier. 



(4) Certain eucalypts and acacias possess seedling and 

 adult forms so unlike as to cause the diverse forms exhibited 

 by the same plant to appear as distinct species. A 

 ■significant point in this connection is that the eucalypts 

 which exhibit this peculiarity are mostly, if not entirely, 

 confined to the highland and coastal region. 



(5) Certain isolated plateau blocks possess species of 

 eucalypts peculiar to themselves. 



(7) Certain eucalypts occur only in isolated patches 

 along the Eastern Highlands. 



No biologist can afford to lose sight of the topographical 

 revolutions at the close of the Tertiary Period. During 

 the Pliocene the evidence points to the existence of apene- 

 plain across Eastern Australia, possessing a mild and fairly 

 uniform climate. In the same period came the formation of 

 the "lead" channels, and later again came the subsidence 

 and burial of these channels with waste and with basaltic 

 lavas. To this succeeded the Kosciusko Period, during 

 which time a great system of highlands was developed peri- 

 pherally to the coastline from Thursday Island to South- 

 western Victoria. The movement was relatively rapid, 

 (see chapter on Physical significance). In no one place 

 was the plateau less than 1,200 feet in height, while the 

 average height was 3,000 feet, and immense blocks of 

 meridional disposition from 4,000 to 7,000 feet in height 

 also formed. By this means the coastal area was isolated 

 from the interior. The climate of the eastern fall was 

 rendered more mild and humid, while at the same time the 



