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scarce ; the only exceptions are Turhinaria ornata, which is fairly frequent 
both on the coral reefs atid on the sandstone ledges ; Padina pavonia, 
more common on the exposed sandstone reefs but less frequent on the 
coral than Turhinaria ; and Sargassum ilicifolium, which is the only really 
common seaweed and which occurs in great meadows at the outer margins 
of the fringing reefs and sandstone ledges that are exposed at low-tide, as 
well as in the deeper water beyond. 
Reefs such as those desci-ibed are extremely common in all the 
islands of the Andaman and Ricobars groups that the writer has visited, 
and the marine vegetation is remarkably uniform in appearance as well 
as in specific constituents. On Car Kicobar, for example, as well as on 
Rutland Island, at the extreme south end of the Andaman main group, 
localities which the writer has visited on different occasions, it is 
hardly possible to detect a species not represented on the reefs of the 
Cocos. On similar I’eefs in South Andaman, however, a second species of 
Cymodocea, quite as profuse where it exists, but more local in its occur¬ 
rence, has been gathered, and on a similar reef in Little Andaman large 
meadows of Halophila ovalis were found associated with those of Gymo- 
docea. The beach between such a reef and the Pandanus sea-fence con¬ 
sists, so far as the winter’s observations extend, almost exclusively of 
coral sand mixed with small shells or fine fragments of large shells. The 
heavy surf in such a bay as this breaks at the outer margin of the reef, 
and even at high-tide in rough weather the swell is so weakened there 
that the waves which break on the beach are not so heavy as to have 
any great erosive power. Indeed their effect appears to be on the whole 
accretive, for the sand that accumulates at the head of the bay becomes 
bound by Ipomoea biloba, Sesuvium, Euphorbia Atoto, etc., the Pandanus 
fence encroaches on the beds of Ipomoea; the coco-nut zone widens sea¬ 
wards, and behind it the first line of beach-forest, containing Terminalia, 
Eernandia, Erythrina, Pongamia, Stephegyne, Thespesia, and the second 
line of the same forest, characterised by Mimusops, Gyrocarpus, Pisonia, 
Ardisia, Gycas assert themselves in an area previously covered by the 
tides. In certain situations, too, the true mangroves stalk forwai’d into 
the tolerably quiet waters of these bays, while in a different but equally 
effective manner, by sending up suckers from among its curious pith-like 
roots, Avicennia establishes itself upon the reef. The guyed and stilted 
habit of the former makes their position very secure; the latter, 
from the enormous area covered by its roots, must also be difficult to 
overthrow. The process of land-making behind a fringing reef, either 
as a sandy flat covered with coco-nut trees, or as a mangrove swamp 
spreading seawards, is well exemplified in the two bays lying respec¬ 
tively to the south and to the north of the position of the first season’s 
98 
