158 A NATURALIST IN THE PACIFIC chap. 



Dr. Warburg in his monograph. Observers Hke myself obtain 

 little peeps into the conditions of existence of these interesting 

 plants ; and the travelled botanist, who becomes a systematist 

 in his later years, attains to a far more extensive view, yet even 

 he can only penetrate the mystery for a little way. 



It is doubtful whether Pandanus odoratissimus, the shore-tree 

 of the tropical beaches of the islands of the Pacific and Indian 

 oceans, of Australia, Malaya, and Southern Asia, can aid us much 

 in any one locality, since its distribution has no doubt been often 

 assisted by man. Yet it is probable that the currents have played 

 a predominant part in its dispersal. Its fruits occur commonly 

 in beach-drift, both in the Indian and Pacific oceans, and are 

 often incrusted with serpulae, polyzoa, and cirripedes. At certain 

 seasons the currents bring them to Keeling Atoll in abundance. 

 When, however, we come to inquire why it is that this beach 

 species is the only representative of the genus in Hawaii and 

 Tahiti, we are met with the possibility of its having been introduced 

 by the aborigines. The tree is almost as useful to a Polynesian as 

 the coco-nut palm, and it has been cultivated by him in some of 

 the atoll-groups, as in the Marshall and in the Radack archipela- 

 goes. In Chapter VII. good reasons are advanced for regarding it 

 as an aboriginal introduction into Hawaii. When, therefore, we 

 learn that in the group just named it extends from the sea-coast 

 to nearly 2,000 feet above the sea, that in Samoa it may at 

 times be found at a similar elevation though usually restricted to 

 the sea-border, and that in the same way in Tahiti and in Fiji 

 it may leave the coast-region and extend into the heart of the 

 islands, we are not inclined to look for any marked differentiation 

 in its character. This indeed appears to be the case. Numerous 

 varieties in different regions are referred to by Dr. Warburg ; but 

 the only important one in the Pacific islands here mentioned is 

 a cultivated form from the Marshall Group. A variety from 

 Hawaii is distinguished chiefly by the smaller size of its drupes. 



Assuming, therefore, that the inland species are as a rule 

 not derived from littoral species originally brought by the currents, 

 and that no birds of our own time are in the habit of carrying the 

 drupes of Pandanus to oceanic islands, in order to explain the 

 distribution of such species we have to choose between the 

 possibility of the agency of extinct Columba^ and birds similar 

 in their habits and the alternative of a continental connection. 

 Dr. Warburg, who says but little of the mode of dispersal of 

 Pandanus drupes, regards the genus as having now two centres, 



