s 
The major demarcation in the vegetation zones of the dry islands 
i§°:£ound aj^lie l> elevation Vf'''the lagoon and proceeds to the top of 
the fe. inner slopes. Under natural conditions the lagoon basin is at 
sea level or just above - thus some of the lagoons of the dry islands 
have more seepage than others due to the tidal fluctuations and fill 
found in the lagoon. Some of the islands have lagoons which were filled 
in above the level of the sea. Normally around the edges of the lagoon 
id a low flat, often submerged area on which the haiophytic Sesuvium 
forms luxuriant mats. Not more than a half meter above this area one 
finds a transition to a Portulaoa — Lepturub association found in some 
cases on guano soils adjacent tothe lagoon. On the slopes above with 
more depth of soil other herbaceous plants such as Boerhavia and 
Sida form an association. Lepturus is usually found in thick often 
pure stands on the outermost beaches and not uncommonly on the inner 
most edge of the lagoon near seeps. In the case of Bnderbuxy Island 
this concentric ring of species and species associations seems to 
hold true except.in areas where the substrate becomes a limiting 
factor. Sesuvium, for example, is not found on sand beaches except 
in areas where the sand is underlain by a watered hardpan. An area 
2 
a few g& m exists on the NE side of Enderbury in the area where an 
opening to the sea was reported by Wilkes (?)• On Enderbury the importance 
of sandy areas left in the midst of high waverows of coral rubble 
is evident. The groves of Cordia and Toumefortia on the south end 
and the former Cocos pits on both the north and south ends are such 
areas. Such areas apparently marked the- an area of seepage connected 
with the lens and were surrounded with piles of coral rubble. In such 
sites are also found vigorous Sida, Ipomoea teba and, in such areas 
with sandy sides, Triumfetta. 
