HILL TOPS TN OEYLOl^. 135 



This list is not to be regarded as absolutely accurate, for so 

 much forest clearance has gone on that it is possible that some 

 of the species once had a wider range. Thwaites's work, upon 

 which most of our knowledge of the Ceylon flora rests, was, 

 however, mostly done before there was much clearance, and 

 most of the isolated hill tops are to this day covered with 

 forest. One can never, of course, except in rare instances, be 

 absolutely certain that a given plant does not occur in a given 

 place, especially in the mixed vegetation of the tropics. The 

 fact, however, stands clearly out that, although so near 

 together, the mountains of Ceylon are like so many oceanic 

 islands, being almost as marked in the possession of local 

 species as if they were fairly far apart in mid-ocean. 



From this we may conclude that there is nothing peculiar in 

 the existence of an oceanic island that should give rise to new 

 species other than the qualities that it shares with mountain 

 tops. Of these, the most obvious is isolation, and we may. I 

 think, justly draw the conclusion that has often been put 

 forward, and say that isolation, as isolation, favours the 

 production of new forms. 



This may be confirmed, as was done in the case of the single 

 mountain Ritigala, by an examination of the methods of 

 distribution of the plants. Opposite to each in the table is 

 given the mode in which it is distributed from place to place, 

 whether by wind (W), birds or animals (A), or by some 

 accidental method (D). It will be seen that there are Wind 7,_ 

 Animals 27, Doubtful 74. 



An approximate comparison with the entire flora of Ceylon 



too small differences to base any conclusions upon, except that 

 possibly the wind-carried plants arrive more often, and so are 

 in a sense less " isolated." 



The same phenomenon as is shown in Ceylon occurs also, so 

 far as a cursory examination shows, in South India and in the 



