394 



BOTANICAL GEOGRAPHY. 



With respect to plaots, the most generally diffused genera, are 

 perhaps aquatic, but the species are seldom if ever identical. It is 

 curious that no Nymphseaceous plant is known in any Indian hill 

 flora, yet from their indicating northernism by extending widely 

 over the plains, they might be expected at least to rise to corre- 

 sponding elevations above them on mountains. The discovery of 

 Hydropeltis in India, destroys one of the exceptions, nor is there 

 now a single aquatic order of plants in any part of the world, 

 which has not a representative with us. ? 



Plants of very high latitudes, require corresponding high eleva- 

 tions to cause their appearance, at, or near the tropics. 



Thus the genera found constituting the flora of Melville Island, 

 may be expected to be deficient on the highest land known to us 

 near the equator, at least the extreme altitude required for their 

 existence at the equator, would necessarily be very great, perhaps 

 greater than we may really know to occur. Yet it is to great eleva- 

 tion in such low latitudes, that we are to look for our deficient genera. 



Apres tout, much, very much remains to be done in India, in this 

 branch of enquiry. Two thirds of the plants hitherto collected are 

 herbaceous or shruby, I mean of such a size that they are easily ac- 

 cessible. It must have often been a source of regret to every col- 

 lector, to be compeled to leave behind so many plants, rendered 

 inaccessible to him from their size. It is only to persons who 

 are stationary, and where good climbers can be obtained, that the 

 whole of a given flora is to be considered accessible. The difficulty 

 of getting flowered specimens of lofty trees, in the ordinary hurried 

 travels of most collectors, is quite insuperable. 



The most distinct region of our flora, is afforded by the dry arid 

 geological structure, frequently presenting volcanic characters; and 

 although these localities, or Botanical Provinces, may be widely re- 

 mote, and separated by tacts of totally different configuration, 

 presenting the maximum of a humid flora, yet the same features 

 are always to be identified. Such are the tracts along the Irrawad- 

 di, from above Ava to Prome, the Coromandel coast, a large portion 

 of Central India, and the north-western Provinces of British In- 

 dia. These tracts are distinguished by the number of Mango, 

 Tamarind, and Palmyras trees, fleshy Euphorbias and prickly pears. 

 The wild vegetation is stunted, and almost invariably prickly, Bala- 

 nites, Ximenia, Miraoseae. Ziziphi, Parkin soni a, Mudar, etc. 



