( 19 ) 
Pandmophyllum Zeylanicum , Macpherson’s Straits, and on a ridge north 
of Viper Island.— Sandstone and Serpentine rock, 
Fimbristylis Andamanica , Middle Andaman.— Indurated chloritic rock. 
Clitoris digitata , ridge at Port Mouat.— Sandstone. 
Lindscea davallioides } on a ridge north of Viper.— Sandstone. 
Pteris tripartita ? north of Mangrove Bay .—Indurated chloritic rock. 
Adiantum lunulatum> on a ridge at Port Mouat.— Clay. 
Lygodivm sp. —Escape Bay.— Serpentine rock . 
21. A considerable diminution, principally of shrubby species, but 
Proportion of the species along the even of trees, can be observed whenever we leave 
coasts to that of the interior. the coast zone. The various trees we see there 
covered with numerous climbers and epiphytic plants gradually become scarcer 
in the interior, where Dinochloa and different Calami become the prevalent 
features. Orchids, winch cover the trees in the mangrove swamps nearly to the 
ground, occur here only on the highest branches and in a very small number. 
To this an exception must be noted, namely, a great part of the forests 
around Port Blair, which are much favored by the form of the land which 
is intersected by the sea. 
The time, however, was unfortunately too short to enable me to explore 
the interior satisfactorily, so as to be able to give accurate statements of the 
proportion of the coast flora to that of the interior. All I can do here 
is to direct the attention of future investigators to this point. 
In considering this apparently gradual diminution of species towards the 
interior, together with the sinking state of the islands, I am inclined to ascribe 
the profusion of species along the shore and in the coast zone to a gradual 
and slow retirement of the different species towards the interior. We may 
presume that a great number of species, which originally grew on the 
countries now submerged between these islands, Burma and Hindoostan, 
have been repelled by the advancing sea, and the vegetation became thus 
comparatively richer in generic types as the area grew smaller. 
Hundreds of species may have been extinguished by this struggle against 
the sea and subsequent change of climate, or may have been superseded by 
more durable ones. The great scarcity of perennials and annuals might have 
originated by the gradual diminution of fresh water as the sea reached the 
higher ridges of the mountains now submerged. 
In Middle Straits, where I already noted that the sinking of the land 
is well marked, we are enabled at some places to see how the beach vege¬ 
tation, now submerged, but still recognizable, has retired behind the mangrove 
formation. North and north-west of Mangrove Bay the gradual transform¬ 
ation of the level lands into mangrove swamps can be easily studied, as 
also the interesting struggle of non-saltmarsh species against the swamps, 
and their retirement towards the drier forests. It is not in the power of a 
traveller to give accurate statistics of such changes, but such investigations 
must be carried out by local botanists, who are enabled to follow the changes 
of the vegetation on a tract of land during a long series of years. 
25. The number of phanerogamic plants noted by me as reallyindi- 
probabie number of phanerogams genous is only 520 species. This, however, is only 
indigenous on the Andamans. an approximation to the actual number existing on 
the islands. 
