14 
THE VEGETATION OF THE DISTRICT OF 
up with the fringe of sedges Pistia Stratiotes occurs in great abun- 
dance, as well as Nymphsea Lotus , N. stellala ) Nelumbium specio~ 
sum> Limnanthemum indtcum , Utricularia flexuosa , U. exoletai 
Ceratophyllum demersum ) Hydrilla verticillata ) V allisnema 
spiralis , Lemna polyrhiza ) Wolffia arrhiza ) Potamogeton indicust 
Azolla pinnata , Marsilea quadrifoliata } etc. In Salin lake miniature 
floating islands composed chiefly of Cyperus platystylis and 
Eleocheris capitata are common. 
The exposed sand banks and sandy spits of the Irawaddy are 
absolutely devoid of vegetation save for an occasional tamarisk. 
The foregoing account makes it evident that there are well 
marked and in the main very natural differences in the character of 
the vegetation of the three zones. Those differences, however, are 
probably not all of precisely equal value. There can be no question 
that the difference between the flora of the Arracan-Nwamadaung 
zone and that of the desert zone is entirely natural and dependent on 
the difference of altitude of, and the different climatic conditions 
prevailing in the two zones. The difference between the desert zone 
and alluvial belt floras is also in essentials a natural one. but 
less due to purely climatic causes, as the elevation and rainfall are 
practically the same for both zones. The determining factor of the 
difference in this case is the Irawaddy. Its waters permeate the 
alluvial belt and allow many species, especially those of a herbaceous 
habit, to flourish, which could not exist or at least would have a very 
hard struggle for life beyond the zone of its beneficent influence. 
Amongst such species may be mentioned Ranunculus sceleratus , 
Cardiospennum Halicacabum . Melilotus alba ) Grangea maderas - 
fatana ) Xanthium Strumarium , Vandcllia , Rumex ) Rosa tnvolu - 
crata , Combretum trifoliatum , Xanthophyllum glaucum t and many 
Cyperacese and Gramineae . 
There is no doubt also that the influence of the Irawaddy acts in 
the opposite direction in being unfavourable to the spread of 
typically xerophilous plants such as Euphorbia antiquorum and the 
various species of Capparis from the desert zone on to the alluvial 
belt. One, however, must not lay too much stress on this aspect of 
the Irawaddy’s influence, as another factor— human agency — inter- 
feres here. It is probable that a good few species typical of the 
desert zone would not find even under absolutely natural conditions 
the alluvial belt by any means a congenial habitat and would probably 
decline to grow there. On the other hand, there is no doubt that 
some species have to put up with life in the desert zone not 
necessarily because they prefer it, but because the human cultivators 
