1891.] D. Prain — The Vegetation of the Coco Group. 405 



relationship that the Andaman-Nicobar chain bears to Inc"o-China and 

 the Malay Archipelago, and perhaps neither it nor the Andamans ought 

 to be spoken of as physiographically a part either of Indo-China or 

 of Malaya ;* these 20 species cannot therefore be cited as indicating 

 either an Indo-Chinese or a Malayan influence. The purely Indian 

 Sterculia villosa must obviously be similarly excluded ; there are therefore 

 21 species, or 32 per cent, of this group, that afford no evidence either 

 way. 



Of the remaining species, one-half, i. e., 23 species, or 35 per cent. 

 of the whole, occur both in Indo-China and Malaya ; these also give no 

 evidence as regards this question. Of the other 23, 15 extend from 

 Indo-China to these islands (some of them, like Dendrocalamus strictus, 

 not going further than the Coco Grroup), without extending to Malaya; 

 while only 8 extend from Malaya to these islands without occurring in 

 Indo-China. The " remanent " species, therefore, so far as this evidence 

 goes, indicate the predominance of an Indo-Chinese element, a fact 

 that is altogether ia accordance with what we should expect from our 

 knowledge of the configuration of the sea-bottom along the line of islands 

 from Cape Negrais in Arracan to the Nias Islands and Sumatra. 



Reviewing the results of the preceding paragraphs we conclude that 

 288 species, or 80 per cent, of the flora, may conceivably have been in- 

 troduced: 33 species, or 9 per cent., by human agency ; 9± species, or 

 28 per cent., by birds ; 60 species, or 17 per cent., by winds and JOl 

 species, or 28 per cent., by the sea. We flnd moreover that the evidence 

 is in favour of the bird-introduced species having, so far as those 

 br-ought by wading- and water-birds are concerned, been introduced 

 from the north, and so far as those brought by frugivorous and by seed- 

 er grain-eating birds are concerned, having come in almost equal numbers 

 from Malaya or the Andamans to the south, and from Indo-China to 

 the north. So far as wind-introduced species are concerned the influence 

 of the north-east monsoon is apparently the more active ; so far as the 

 sea-introduced species are concerned the influence of currents from 

 Malayan seas to the south-east has been paramount. 



The subjoined table gives a synoptic view of the probable origin 

 of the Coco Island flora, 



* The writer has proposed the name " Malay Isthmus " for the conjoint area 

 that includes Tenasserim, the Andamans and the Nicobars, and believes that it will 

 be found convenient to recognise this as a distinct phytogeographical subdistricfc. See 

 Ann. Boy, Bot. Garden^ Calcutta, iii, 238. 



