INTRODUCTION. XXxi 
they no more exist in nature than do absolute differential characters between many 
natural orders or genera of plants; but Drude has too many and unnecessarily unequal 
regions. Several of them correspond, or very nearly so, to the secondary divisions of 
other writers, and are not unnatural in this sense; yet we do not agree with the author 
in raising them to primary rank. On the other hand, his Indian region embraces 
tropical Asia, the whole of the Pacific Islands, from New Caledonia to the Sandwich 
Islands, and a large area of North Australia. It is unnecessary to dwell upon the 
great disparity of this region as compared with his East-African Islands region, or his 
New Zealand region of the same rank. 
With regard to the Flora of the Sandwich Islands, it is so highly specialized, and 
its affinities so complex, that it cannot be included in any primary region without 
the question arising whether it might not with equal propriety have been included in 
another, as will hereafter be shown. 
The Flora of North Australia undoubtedly contains a large tropical element consisting 
of species, many endemic, of Asiatic genera, or genera of wider range; but the elimi- 
nation of such species as are common sea-shore plants throughout the eastern tropical 
region would considerably reduce this element. It is equally true that some of the 
orders and tribes specially characteristic of the Australian Flora are almost entirely 
wanting, such as the Epacridee, Rhamnaceew, Myoporinee, Boroniee, the Podalyries, 
and some others; but are these two conditions sufficiently developed to justify separation 
in a primary division and annexation to the eastern tropical region? Drude appears 
to have separated it because it is tropical. Wherever the boundaries are drawn there 
will be overlapping of different elements to some extent, and a more natural boundary 
in this region is further north. Even if in the north-eastern coast district the com-— 
position of the vegetation is more Asiatic in character, it is not so in the north-west. 
Whatever the amount of infusion of Asiatic types may be in North Australia, and 
whatever groups are wanting or rare, the highly characteristic Australian gum-trees 
(Eucalyptus) and the phyllodineous Acacias are represented respectively by twenty-five 
and sixty-seven species ; Proteacez by about thirty-five species; Stylidiew and Goode- 
niaceee combined by upwards of fifty species; Amarantaceee by nearly sixty species; 
capsular Myrtacee, exclusive of Eucalyptus, by about thirty species; and many 
characteristic Australian genera, such as Dodonea and Stackhousia, are also present, 
though numerically few. 
There seems even less reason for including New Caledonia in the Indian region, 
for although the Rubiacez and sarcocarpous Myrtacez appear to be the dominating 
groups, yet the vegetation generally is more Australian than tropical Asiatic in 
character. As Baron Mueller observes *, New Caledonia is the only country outside 
of Australia where capsular Myrtacee are largely developed, though they include 
* A Lecture on the Flora of Australia, 1882, p. 16. 
