I,—INTRODUCTION. 17 
great dissimilarity; we are now in a land where the turf is 
uniformly perennial, a circumstance that carries with it more 
than lies on the surface. The northern portion includes the sub- 
montane forest belt; in this respect North Bengal. accidentally 
differs from Tirhut, since along the northern border of that province 
this forest lies largely within the Nepalese frontier, and so is removed 
politically from the area with which we have to deal. It is this 
Subhimalayan forest which supplies the feature that necessitates 
the separation of North Bengal from the rest of the Lower Gangetic 
Plain. Our knowledge of the flora of North Bengal, as regards the 
central portions, we owe chiefly to Kurz, King, and Clarke; the 
most westerly district, Purnea, has been well explored only by 
Buchanan-Hamilton, few of whose specimens, unfortunately, are 
available in India. The submontane forest has been explored by 
Anderson, King, Kurz, Clarke, and Gamble, but the attention of 
all save the last-named botanist, and indeed his also in the main 
has been directed to the Terai, which, for reasons already set forth, 
it has been necessary to exclude from the scope of this work. The 
Duars, which are merely an eastward extension across the Tista 
of the same forest belt, have been, however, oes explored by 
Gamble, and more fully examined by Hea and by Hai 
to whose exertions our knowledge of the region is chiefly due. 
Much, however, yet remains to be done both in the Duars and in 
Cooch Behar. 
Central Bengal, the tract to the south and west of the Ganges 
and Brahmaputra, lying north of the Sundribuns and east of the 
Bhagirati and Hughli, possesses, as compared with the three 
Bengal tracts already discussed, the negative feature of being 
typically representative of the alluvial deltaic rice-plain and nothing 
more. Except that along the banks of its main streams, so far as 
these are at all affected by the tides, we find, as a narrow hedge or 
in scattered patches, some species characteristic of the Sundribuns, 
and that all abandoned river-beds and ponds are covered with 
water-plants, the whole country is a semi-aquatie rice-plain. 
The mounds and embankments thrown up here and there through- 
out the area are, where not occupied by honses or by age 
shrubberies. Of this tract, as of the Sundribuns, we possess a 
knowledge that is probably practically complete. Little or nothing 
