166 A NATURALIST IN THE PACIFIC CHAP. 



belong, derives support from the singular fact in the distribution of 

 the order pointed out by Mr. Hemsley, that it is wanting in many 

 oceanic islands where there is no littoral flora. 



In one genus, Guettarda, the inland species are regarded as 

 having been sometimes developed independently of the coast 

 species, and as at other times derived from it, both principles 

 having been at work in Fiji and only the last in Tahiti. 



In two genera, Pandanus and Barringtonia, which represent the 

 " Fijian difficulty," there is no reason on grounds of affinity to 

 connect the inland with the coast species ; and since the agency of 

 existing birds is improbable in the first genus and out of the 

 question in the second, whilst the operation of the currents is 

 excluded for the inland species of both genera, it is assumed that 

 we must either appeal to the agency of extinct birds, such as those 

 of the Mascarene Islands, or we must fall back on the hypothesis 

 of a continental connection. In the instance of Barringtonia it is 

 also possible that some of the inland species may have been derived 

 from species spread through cultivation. 



Lastly, in three genera (Eugenia, Drymispermum, Acacia) the 

 coast species are viewed as derivatives of the inland flora in the 

 Western Pacific, not necessarily in Fiji, but it may be in New 

 Caledonia or in one of the other large groups. In this case the 

 coast species of all three genera are either unfitted for dispersal by 

 currents, or display the capacity only in a small degree. 



We thus see that in only seven of these twenty-two genera, 

 containing both littoral and inland species in the Pacific islands, 

 can it be argued from the standpoint of dispersal that the inland 

 species are or may have been derived from the shore species ; and in 

 most instances the evidence is largely presumptive in its character. 

 In three genera the reverse has been the case, and here the coast has 

 borrowed from the inland flora, In twelve, or more than half of the 

 genera, the shore and inland species have been evidently inde- 

 pendent in their origin. It is accordingly apparent that in the 

 Pacific the strand flora has lent more to the inland flora than it has 

 borrowed from it ; but with a large proportion of these coast genera 

 no interchange has taken place. Two-thirds of the genera of the 

 beach-plants have no inland species, and in their case the question 

 of such a connection cannot be raised. With the remaining genera 

 such a relation can be suggested in only two-fifths of the cases, or 

 in about one-seventh of the total number of beach genera. Where 

 a connection can be traced, it points more frequently to the deriva- 

 tion of the inland from the shore plant. Taking all the evidence 



