FLORA OF THI7 SUNDRIBUNS. 
253 
the actual neighbourhood of the excavation. On the other hand, we 
find places well to the south of the northern limits of the existing 
Sundri-forest where, on steep banks that are subject to erosion, a 
layer of broken bricks and pottery is being exposed at a level well be- 
low that of the high tides of the rainy season. Whether these facts, 
taken in conjunction, indicate that the Sundribun area has been sub- 
jected to alternations of elevation and subsidence is an open question. 
Whatever may be the truth in this respect there is no doubt that all 
of the surface soil in the lower Gangetic delta is newly-formed land. 
This being the case, there can be no such thing in the Sundribun 
forests, savannahs or clearings as an indigenous species. The nature 
of the flora, with its extraordinary proportion of genera and even of 
natural families that, so far as this region is concerned, are monotypic, 
points to the same conclusion. An examination of the Sundribun 
flora therefore resolves itself into a discussion of the dispersal 
-and the distribution of its species ; a study of how and whence the 
plants now present in the area have been introduced. The simplest 
method of dealing with the problems involved is to deal first with 
the dispersal of these species and to commence with those plants 
that inhabit the swamp-forests and constitute the more characteristic 
part of the flora. The different possible agencies of dispersal may 
be accepted as (i) Human^ by which the introduction may have been 
[a] intentional^ as in the case of cultivated or planted species, and 
{h) inadvertent^ as in the case of weeds of fields or w^aste-places 
( 3 ^) Bird, and then either {a) by water-hirds that carry seeds of small 
size or, rarely, spores attached to their feet, or to the feathers near the 
case of their bills, along with pellets of mud; or (b) by fruit-eating 
birds that void uninjured the seeds of fleshy fruits or seeds provided 
with a mace : (3) Wind, carrying seeds or spores that are sufficiently 
small and light, or seeds or fruits provided with wing-like expansions, 
or with a coma or pappus, that may act as a parachute : (4) River^ 
bringing down from the Indian Hills or from the Gangetic plain seeds 
and fruits of various kinds : (5) Sea, bringing, by means of currents 
and tides, the seeds and fruits of, usually, littoral species from other 
shores. 
, Swamp-Forests.— Species introduced by man whether by accident 
or by design, are not to be expected in the swamp-forests : the only 
unequivocal instance is Odina Wodier, a species planted in existing 
clearings and plentiful where there are vestiges of former occupation ; 
this was also obtained by the writer at a small camping-ground used 
by wood-cutters on the bank of the Ambaria khal. Nor are species 
likely to be introduced by water-birds to be expected in these forests; 
none have so far been found. Species in all probability introduced 
