40 HERBARIUM OF THE CALCUTTA BOTANIC GARDEN. 



In Southern India the temperate Flora begins about 7000 feet of 

 elevation, but as we advance northward, the requisite elevation gradu- 

 ally diminishes till in the most northern part of the Himalaya it is not 

 more than 4000 feet. In Southern India therefore the temperate Flora 

 is found only in isolated patches on the mountain-tops, but along the 

 Himalaya it is continuous from one end of the chain to the other. 

 Here it presents three distinct types, the first of which is the normal 

 Himalayan type, of forms which are adapted to a climate dry at one 

 season, wet at another, occupying the Central Himalaya. To the west 

 we have the European type intruding upon and mingling with it, espe- 

 cially in the inner ranges, where the climate is drier. To the east the 

 Japan or moist temperate Flora is especially developed in Khasia and 

 Sikkim, where the climate, 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 Ganges, which stretches from sea to sea, has a gradually 

 diminishing rain-fall as we ascend the Ganges and approach the Indus. 



The rain-fall is also greater every where near the base of the Himalaya, 

 and diminishes as we recede from it. In Sindh and the Western Pan- 

 jab no rain falls, and there we find an arid Flora, identical with that of 

 Egypt, with which in fact it is continuous 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 south-west 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 aloi 

 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 intense heat 

 of May and June, burst into life with renewed vigour at the commence- 

 ment of the rains. 



