Oliver. — Vegetatiori of the Kermadec Islands. • 155 



The floras of Lord Howe and Norfolk Islands are fragments of the larger 

 one which migrated from Malaya by this way to New Zealand, received 

 from the continental bridge stretching between New Caledonia and New 

 Zealand, before it disappeared beneath the surface of the sea ; together 

 with a number of Australian forms which have arrived from time to time 

 across the intervening space of ocean. 



' The Kermadec Islands have received their plants by transoceanic- 

 migration mainly from New Zealand, but also from Norfolk Island and 

 Polynesia (see 1 ; p. 163). They are younger than Norfolk or Lord Howe 

 Islands, but are attached to them because of the large community of species 

 of plants with, and the possession of genera and species characteristic of, 

 those islands. 



The three groups of islands possess insular floras, are properly included 

 in the New Zealand biological region, and together forzn a subregion for 

 which is proposed the name " subtropical islands province," in contra- 

 distinction to Dr. Cockayne's " subantarctic islands province." 



(c.) The Formations. 



On an oceanic island which depends for its stock of plants on accidental 

 migrations the flora is necessarily of a fragmentary character, and dift'erent 

 forms arriving from various directions compete with one another for the 

 ground. Thus a plant taking a minor part in a formation in the land of 

 its origin may in its new home be able to compete successfully with the 

 plants from other countries with which it comes in contact, ahd take a 

 leading part in some formation. Where a small island in mid-ocean, such 

 as Simday Island, has received its plants from two or three ecjuidistant 

 fully stocked areas containing widely different assemblages of plants, one 

 might expect the resultant plant formations to be new combinations of 

 species. The affinities of the two most characteristic of the Sunday Island 

 plant formations — forest and gravel flat — will be considered Ijriefly here. 

 In both New Zealand, Polynesian, and Lord Howe - Norfolk Island forms 

 mingle in plant-communities which from the diverse origin of their con- 

 stituents are peculiar. 



The three principal plants of the gravel flat in Denham Bay are Ipomosa 

 pes caprce, Mariscus xistulatus, and Scirpus nodosus. The first is a common 

 shore-plant in most tropical countries ; it occurs in Lord Howe and Nor- 

 folk Islands, but not in New Zealand. Mariscus ustulatus is confined to 

 New Zealand ; whilst Scirpus nodosus is found in New Zealand, Lord Howe 

 and Norfolk Islands, but not in Polynesia. 



Metrosideros villosa. the principal forest-tree on Sunday Island, is dis- 

 tributed throughout Polynesia, from New Caledonia to Tahiti and the 

 Sandwich Islands, and also on Lord Howe Island. Should it on any of 

 the Pacific islands take a leading part in a forest, there might be a super- 

 ficial resemblance between this formation and the forest on Sunday Island ; 

 but the principal species of trees associated with it could not be identical 

 with more than one or two of those on Sunday Island. Bhopalostylis Baueri, 

 an important member of the Sunday Island forest, occurs elsewhere on 

 Norfolk Island only. Rapanea kermadecensis ar.d Boehmeria dealhata are 

 peculiar to the Kermadecs, but closely related to Norfolk Island plants. 

 Corynocarpus Icevigata, Myoporum Icetum, Nothopanax arhoreum. Melicope 

 ternata, and Pittosporum crassifolium are endemic New Zealand species. 

 The two species of Cyathea, and Ascarina lanceolata, while not occurring m 



