1856.] Herlarium, of the Calcutta Botanic Garden, 417 



throughout the year, or at least throughout the whole period of 

 vegetation, is extremely moist. 



The tropical flora is dependent in like manner upon the climate, 

 and partially also on the nature of the surface. The open plain of 

 the Indus and Gauges which stretches from sea to sea, has a gra- 

 dually diminishing rain-fall as we ascend the Ganges and approach 

 the Indus. The rain-fall is also greater everywhere near the base 

 of the Himalaya and diminishes as we recede from it. In Sindh 

 and the Western Panjab no rain falls, and there we find an arid 

 flora identical with that of Egypt, with which in fact it is continu- 

 ous across Arabia and Southern Persia. The characteristic plants 

 of this arid flora extend at a distance from the mountains down the 

 valley of the Ganges, but never approach the more humid Himalaya, 

 in which we have a flora like that of Bengal, though they recur 

 in the Deccan and Carnatic, which are sheltered from the moist 

 wind of the S. W. monsoon by the higher ranges of the Ghats. 



In the hilly districts of India where a dry hot season is succeeded 

 by more or less heavy rain during the monsoon, we find in all parts 

 of the empire a very similar flora. On the eastern slopes of the 

 Ghats, in the valleys of Nagpore, on the slopes of the Arawali, and 

 along the base of the Himalaya (except to the eastward and in the 

 extreme west) we find the same monotonous forest consisting 

 partly of evergreen and partly of deciduous leaved trees with many 

 creepers. The trees are gay with flowers in spring, and after being 

 scorched by the inteuse heat of May and June burst into life with 

 renewed vigour at the commencement of the rains. 



It is ouly when the humidity begins to linger in the damp and 

 shady valleys throughout the year that the flora changes its cha- 

 racter. This we find to be the case in many parts of the valley of 

 the Nerbada, and in the deeper ravines of the Ghats of the Concan . 

 The number of peculiar forms iucreases as we go southward, and 

 is very great in the forests of Travaucore and Ceylon. So in the 

 Central Himalaya, humid forms appear as far west as Kumaon, in- 

 crease in numbers in Nipal, predominate in Sikkiin and are univer- 

 sal in Assam. In Malaya where the climate is humid at all seasons 

 we have the flora of the Archipelago, the richest and most varied 

 which is fouud in any pari of India. 



3 i 2 



