The major demarcation in the vegetation zones of the dry islands occur along the elevation of the lagoon and proceeds to the top of the 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 is a low flat, often submerged area on which the halophytic Sesuvium forms luxuriant mats. Not more than a half meter above this area one finds a transition to a Portulaca - Lepturus association found in some cases on guano soils adjacent to the 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 Enderbury 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 a few m2 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 wavewrows of coral rubble is evident. The groves of Cordia and Tournefortia on the south end and the former Cocos pits on both the north and south ends are such areas. Such areas apparently marked 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 tba and, in such areas with sandy sides, Triumfetta.