AN ISLAND IN THE CHILKA LAKE. 275 



abundant shrub, while the branches of the trees are profusely festooned with the 

 curious swollen and jointed stems of the vine, Vitis quadrangularis. This type of 

 vegetation, for natural causes into which I will enter later, is rapidly being replaced 

 by mixed thickets in which various vines and liaiias are abundant and the 

 Nim {Azadirachta indica) contends for the chief place among the trees with several 

 species of Ficus that have not the spreading habit and adventitious roots of the 

 Banyan. This occurs on parts of the island in which the rocky basis is covered by a 

 thin layer of soil. 



Part of the area we have to consider is, however, sandy and gravelly rather than 

 rocky and soil of this kind is unsuitable for Ficus bengalensis and other fig-trees and 

 also for Glycosmis pentaphylla. In inland spots where rocks are absent or deeply 

 buried in sand there is, therefore, no ficetum and Weihea ceylonica replaces the 

 Glycosmis as the dominant shrub, while the most abundant trees are the Nim and 

 Crataeva religiosa, which here reaches a large size. 



In the inland parts of the island these are the main types of vegetation, but the 

 areas they occupy are almost completely surrounded by a marginal zone of trees of 

 Pongamia glabra, which forms a ring round the island at high flood-level. 



Two less important types of natural vegetation can further be distinguished, that 

 of bare rocks and almost soil-less stony patches in the interior, and that of the littoral 

 zone exposed between the ring of Pongamia- trees and the edge of the water when the 

 autumn floods subside. The former type is, however, poorly developed and little 

 differentiated, while the latter consists mainly of a few small herbs, sedges and grasses 

 and of maritime trailers, such as Ipomaea biloha, which attempt to gain a footing at 

 certain sandy spots on the shore every year, but never succeed in establishing them- 

 selves firmly. 



Types of vegetation, due to the interference of man, now occupy certain parts of 

 the island, though there is no actual cultivation. Of these, two can be recognized, 

 viz. {a) thickets of the large leguminous herbs, Crotalaria striata and Tephrosia 

 purpurea, growing on soil from which all other plants have been removed, and ip) the 

 scanty growth of dwarf grasses, sedges and other plants which spring up on ground 

 that has been levelled and practically deprived of soil as well as being cleared. 

 Round the edges of a pond and of a well dug in the rock similar plants appear at first 

 sight to constitute a third type, but the species are for the most part the same, only 

 more vigorous and as a rule more erect. 



Finally, it should be noted in this general account of the vegetation of the 

 island that several exotic plants are feral and abundant and have conspicuously 

 altered its facies. The chief of these are the Prickly Pear {Opuntia sp.), which 

 seems to be replacing the indigenous giant Euphorbias, the Custard Apple {Anona 

 squamosa), a very abundant large shrub or small tree, and Jatropha gossypifolia, one 

 of the commonest of the larger herbaceous plants. 



The various types of vegetation will be considered separately in greater detail, 

 but a comparison of the flora and vegetation as a whole with those of the neigh- 

 bouring islands and headlands may first be made. 



