504 A NATURALIST IN THE PACIFIC chap. 



Dispersion then was general over the Pacific. The distribution of 

 the New Zealand and Antarctic genera, plants that take a sub- 

 ordinate part in the floras of the Pacific islands, is regarded as 

 having occurred during the glaciation of the northern hemisphere. 



On the Suspension of the Agencies of Dispersal in the Tropical 

 Pacific. — If the remark of Drake del Castillo that genera possessing 

 only non-endemic species in the Pacific islands owe their presence 

 in this region to existing agencies of dispersal looks something like 

 a truism, we must remember that, assuming Nature to be uniform 

 in her methods, it involves not merely the original co-operation of 

 the same agencies with genera that own only peculiar species, but 

 also the subsequent suspension of the work of these agencies. 



The nature of the connection between freedom of dispersal and 

 specific differentiation is well brought out by Beccari in contrasting 

 the species of Ficus and the palms of Borneo ; whilst out of fifty- 

 five species of Ficus collected by him in that island, 30 per cent, 

 were apparently peculiar, 85 per cent, of the 130 Borneo palms had 

 not been found elsewhere. In the English edition of his Nelle 

 Foreste di Borneo he says that " the explanation lies in the fact of 

 the facile dissemination of the various species of Ficus through the 

 agency of birds, an explanation which applies to all trees which 

 produce edible fruits specially relished by animals." He shows, 

 also, that the same principle applies within the limits of the genus 

 Ficus, since of those Bornean species known to him as belonging 

 to the section Urostigma, which possesses fruits most preferred by 

 birds (pigeons, hornbills, &c.), nearly all (fourteen out of sixteen) are 

 found elsewhere ; whilst of ten species belonging to the section 

 Covellia, where the fruits are more or less hidden and inconspicuous, 

 and with difficulty discovered by birds that would effectively 

 distribute the species, four, at the most, are found elsewhere. 

 " Such facts," he goes on to say, " show that in tropical countries 

 the various kinds of Ficus are, to a large extent, biologically con- 

 nected with birds, which, perhaps, on their part, also owe some of 

 their peculiarities in the shape of the bill or in the plumage to the 

 nature and coloration of the fruits which form their food." 



Whilst Dr. Beccari as a botanist lays especial stress on the 

 biological connection in Malaya between the plant, as illustrated 

 by the genus Ficus, and the bird, Mr. Perkins, as a zoologist, is 

 similarly emphatic on the biological connection in Hawaii between 

 the bird, as illustrated by the peculiar family of the Drepanididae, 

 and the plant. The plants here are the arborescent Lobeliaceae 

 and the Freycinetias. To the flowers of the arborescent Lobeliaceae 



