292 D. Prain — A List of Diamond Island Plants. [No. 4, 



compared with only tivo exclusively Arracan and tivo exclusively Pegu 

 species. The negative evidence, however, points quite the other way, 

 for there are no fewer than eighteen species* indicating the absence of 

 Andaman influence, as against only fivef indicating the absence of 

 Arracan influence, and five^ indicating the absence of Pegu influence. 

 But it has to be kept in mind that the Andaman flora is by no means 

 so well-known as the floras of the other two districts are and this nega- 

 tive evidence may be expected to be decreased, while there is no reason 

 why the positive evidence may not be increased. The figures are in 

 every case too small for special inferences being drawn from them. 



The comparative values of the influences of these three adjacent 

 areas are more accurately determinable from general evidence. In 

 applying this it is necessary to use in succession as numerators the 

 figures yielded by each possible distributional arrangement in which 

 adjacent areas are concerned and as denominators in each case the num- 

 ber of adjacent areas involved ; by adding together the fractions afi^ect- 

 ing particular adjacent districts we obtain a number that indicates the 

 proportional influence of each of them in the composition of the flora of 

 the island. The following are the results : — 



1. Andaman-Nicobar influence -V'+f -|-f =27-f, or 29-29%. 



IT. Pegu-Malayan influence J-O + A -f. j_5 4. |. =34^-, or 36-14%. 



III. Assam-Arracan influence ^+ V' + t + t =^'H, oi' 34-57%. 



95. 100. 



This method of computation may be extended to each of the sub- 

 divisions under the general headings ' habit ' and habitat.' For some 

 of these it is not, however, necessary ; from others no particular informa- 

 tion is to be derived. Under the heading of habitat, however, an 

 analysis of the classes of inland and of coast plants is not without in- 

 terest, especially when their results, expressed as per-centages, are com- 

 pared with those afforded by the general total. They are as follows : — 

 Inland species : — 



Andamans, =^^- + 1 + 1 = 9i or, 2456%. 



Pegu, = ¥- + f + f + f = ^4A or, 39 03%. 



Arracan, = ¥- + f + T + T =I3f or, 36-41%. 



38. 100 00. 



* Obtained by adding together the totals of lines 3, 4 and 7. 

 t Obtained by adding together the totals of lines 2 and 4. 

 X Obtained by adding together the totals of lines 5, 6 and 7. 



