FLORA OF THE SUNDRIBUNS. 
than 32 are represented by only one genus ; while as many as 27 
of these 32 have only one species. Other 15 natural orders are 
represented by only 2 genera; other 7 by only 3 genera; yet another 
7 by only 4 genera. Only 2 natural orders, Scrophularinese and Rubia- 
cessy have 5 genera apiece and 3 orders, Cucurhitacesey Verhenaceas 
and Palmeaey have 6 genera. Of natural orders with more than 6 
genera, Orchidaceae have 8, Cyperaceae and Polypodiaceaa each 9, 
Asclepiadacex and Composite each \ \y Euphorhiaceaa 14, Grami^ 
neae 18, Leguminosae 25. As regards number of species, Leguminosas 
with 38 species leads ; followed by Gramineae with 29 ; Cyperaceas 
with ig] Euphorhtaceae with 16; Polypodiaceae with 14; Orckida- 
ceas with 13; Asclepiadaceas with 12; Convolvulaceas with 9; 
Cucurhitaceae with 7 ; Malvaceasy Rhizophoreas, Ruhiaceas^ Urtica- 
ceae and Palmer each with 6 ; the rest with 5, or fewer than 5. 
Of the 245 genera, no fewer than 190 are represented by only 
one species ; of the remaining 55, as many as 35 have only 2 species ; 
other 1 1 have only 3 species ; other 6 only 4 species each ; one has 
5 species ; only two genera, Ipomosadind Panicum have each 6 species. 
The subjoined table gives a brief resume of the composition of the 
Sundribun flora from the taxonomic point of view : — 
Table I. — Systematic Synopsis of Sundribun Plants, 
Orders. 
Genera. 
Species. 
Thalamiflorse 
10 
18 
20 
Disdflorse 
9 
17 
21 
CalyciflorsE 
10 
46 
64 
Corolliflorse 
19 
63 
86 
Incompletse . 
9 
30 
39 
Monocotyledons . . 
15 
59 
87 
Vascular Cryptogams , 
• • • 
3 
12 
17 
Totals 
• 
75 
245 
334 
IV.-ORIGIN OF THE SUNDRIBUN FLORA. 
The geographical position and the physical condition of the 
Sundribuns show that they are only part of the alluvial plain of Lower 
Bengal, the whole of which is of recent geological formation, and that, 
as a matter of fact, the process of extension of that plain is here going 
on under our eyes. Moreover, when borings are made or deep tanks 
or canals are dug in the Lower Gangetic Plain at a considerable dis- 
tance to the north of the existing Sundribun forests, a layer of soil is 
found at no very great depth in which are present the remains of 
species that now exist in the Sundribuns, but that have retreated from 
