On " Fasciation.^' 55 The mangrove formation is confined to the muddy edges of the tidal estuaries, which were probably at one time completely covered with this vegetation, (where the shores are flat and hence covered at high water) for some miles from the sea. Rhizophora and Britguiera form the largest pure associations, but Sonneratia is practically ubiquitous and goes far up the rivers and on to the mud flats and swamps. Acanthus forms a well-marked zone on the water's edge in very many

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... s. Chrysodinm aiiieum is a very abundant and characteristic riverside feature, usually beginning some little distance from the mouth and mingling with the fresh water reed-marsh formation. It is also extremely common on brackish swamps, often in company with Sonneratia. Nipa (rather rare in Ceylon) has a very similar habitat. A series of transitional species lead from the typical highly adapted mangroves to the Beach-jungle trees, nearly all of which are found where the estuaries have definite banks above water level, and on the edges of the mangrove swamps. Where the banks slope steeply from the water's edge inland forms occur, while the mangroves and semi-mangroves are scanty or absent.