1890.] 



D. Pram — A List of Diamond Island Plants. 



289 



the proportion of forest species to the whole is 30 : 37, or 81 per cent, 

 whereas in the case of the cosmopolitan and almost cosmopolitan species 

 the proportion of forest species to the whole is 10 : 39, or 25f per cent, 

 only. 



To complete the account of the distribution of these species it is 

 necessary to examine their special distribution throughout South- 

 eastern Asia. From this it is possible to compute the relationships of 

 the Diamond Island flora to those of the three adjacent areas Arracan- 

 Assam, Pegu-Malaya, Andainans-Nicobars respectively. 



We find that 77 species are in distribution both Cis-gangetic (i. e., 

 are present in India, or in Ceylon, or both) and Trans-gangetic (i. e., 

 are present in some or all of the three areas whose influences meet in 

 Diamond island). The remaining 17 species are Trans-gangetic only. 

 So that as regards the composition of the Diamond Island flora the 

 Indo-Chinese influence bears to the Indian a proportion of 95 : 77 (or 

 very nearly of 9 : 7) ; in other words the Indo-Chinese influence is -|--§-, 

 or just under 19 per cent, stronger than the Indian. The details of 

 this distribution are more compactly given in the subjoined table. 



Table II. Distribution of the Diamond Island species in S. E. Asia. 

 Species both Cis-gangetic and Trans-gangetic ;— 77 



Common to all the districts , 56 



Absent from a Cis-gangetic district ; — 7 



Absent from Ceylon only . 6 



Absent from India only {Ipomcea denticulata)... 1 



Absent from Trans-gangetic districts; — . 



10 



Absent from Andamans-Nicobars only 8 



Absent from Pegu-Malaya only (Vitex Ne- 



gundo) 1 



[This sp. is only represented in Arracan 



by the Diamond I. gathering] : 

 Absent from both Andaman and Pegu (Bre- 



gea volubilis) 1 



Absent both from a Cis-gangetic and a Trans-gangetic dis- 

 trict ; 



[These sp. are all absent at once from the Andamans 

 and from Cejdon]. 



Species Trans-gangetic only : — 



Common to the three Trans-gangetic districts : 



10 



Distributed throughout Arracan- Assam dis- 

 trict ... 7 



Represented in Arracan by the Diamond I. 

 gathering only ... 3 



18 



Carried over ... 



95 



