400 D. Prain — The Vegetation of the Coco Group. [No 4, 



eastern line. The species that are common to these islands and to 

 Ceylon are more difficult to explain. If we felt certain that they are 

 species of distinctively Ceylonese type and that they occur, out of 

 Ceylon, only in these islands, we might suppose that Ceylon birds are 

 occasionally driven by storms as far as the Coco Group and consider 

 the dispersal of the seeds of such species as one of the indirect sequels 

 of cyclones of unusual severity. The birds even need not be different, 

 as regards species, from those commonly found in the Andamans ; they 

 need only be individuals that have followed the western instead of the 

 eastern line of migration southward, and that under exceptional cir- 

 cumstances have passed directly from one line of migration to the other, 

 carrying in their crops seeds or fruits that ai^e characteristic of the line 

 of migration from which they have been driven. If the species are 

 not of Ceylonese type, their occurrence both in Ceylon and the Cocos 

 may, as has been said already, only indicate that they have been brought 

 directly from Malaya or Australia by southern birds that migrate to Cey- 

 lon as well as to the Coco Group but do not go as far north as peninsular 

 India. 



The remaining sub-group consists of species with seeds or fruits 

 that are eaten by birds of different kinds, not for the sake of any pulpy 

 portion, but on account of the nutritious properties of the whole fruit 

 or seed. We have to realize that the dispersal in this case is not, as in 

 the case of pulpy fruits the seeds of which are afterwards voided, an 

 oi'dinary circumstance, inasmuch as the seeds are eaten for their own 

 Bake and are of necessity digested by the birds that eat them. But 

 though it is not perhaps a common occurrence — the numbers of migrat- 

 ing grain- or seed-eating individuals considered — for newly-arrived 

 birds to be killed, there is no doubt that a certain proportion, tired out 

 by their long flight, must fall victims to raptatorial birds immediately 

 on their arrival, the grains or seeds that their crops may contain 

 falling aside and possibly germinating. Besides this means of introduc- 

 ing such species, and, even if the results be slight, it must nevertheless 

 be in constant operation, there is the further possibility of similar species 

 being introduced during severe cyclones, owing to birds that have been 

 driven to land being captured and devoured, while exhausted by the 

 buffeting of the tempest, by birds or beasts of prey. In this way not 

 only the grain- or seed-eating species that ordinarily visit the islands, 

 but species both of this and of the fruit-eating class that do not usually 

 reach the group, may conceivably arrive and as conceivably bring with 

 them the seeds of plants that birds which are normal visitants have 

 no opportunity of meeting with or may not care to eat. it has to 

 be admitted, however, that species for which this mode of introduction 



