INSULAR FLORAS. 



PART VI. (b). 



IN my article (59) on the flora of the African Islands of 

 the Indian Ocean, I dealt with the subject in consider- 

 able detail, but beyond the vascular cryptogams I had very 

 few data concerning the Isle of Bourbon. Since then 

 Dr. Cordemoy has published a Flora of the island (60), 

 which is a consolidation of all the materials he has been 

 able to collect during the leisure of upwards of thirty years' 

 residence in the island, though unfortunately without a full 

 collation with the rich earlier collections in the Paris Her- 

 barium of Commerson, Du Petit-Thouars, and other botanists. 

 Moreover, he has not worked out the geography of the 

 plants to the extent he might have done, so that it takes 

 some time to find and extract the particulars of special 

 interest to the geographer. Indigenous and naturalised 

 plants are included in the same enumeration without any 

 typographical distinctions ; and the summary is limited to 

 a table showing the number of species of each natural 

 order, including naturalised species. A rough calculation 

 of the number of indigenous species of vascular plants, 

 described or enumerated, gives a total of about 11 00, 

 whereof 200 are ferns, and 172 are orchids.' This is nearly 

 250 higher than Baker's estimate (61) of the vascular plants 

 of Mauritius; but, although the islands are nearly of the same 

 size, the mountains of Bourbon rise to altitudes of between 

 9000 and 10,000 feet, or about 6000 feet above those of 

 Mauritius ; thus giving an additional climatic zone to the 

 former island. And an analysis of the components of the 

 flora shows that Bourbon possesses a much larger temperate 

 element. But it should be known that Cordemoy takes a 

 narrower view of species than Baker, especially in ferns ; 

 and some allowance would have to be made for this in com- 

 paring the totals. Apart from this divergence, the flora of 

 the two islands is essentially the same, several genera and 

 many species being common to both and found nowhere 



