THE COAST-FLORA OF THE CLACTON DISTRICT. 207
3. The ordinary level of the marsh or "saltings."
4. The higher littoral meadow.
In zone (2) Salicornia (in very succulent and richly ramified
forms) and Spartina stricta (Bristle-grass) are the dominant
species. Of common occurrence, especially in the more sheltered
creeks, is Aster tripolium (Sea Aster). Spartina, a stiff, erect
gregarious grass, advances furthest against the tide, forming low-
elevations in the soil of the open beach or fortifying the exposed
bank of some creek. All the three species mentioned are
excellent defenders of the land against the encroachment of
the sea, and in many places they are agents in adding to the
land.
The sea-water rushes into the littoral marsh by a kind of
inverse river-system, formed jointly by the backwash of the
tide and the rain water. The vegetation of the level of the
marsh varies considerably with its height. If it is low enough
to be daily submerged in the tide, as it is the case with the
Walton and Brightlingsea marshes, Poa maritima (the Glyceria
or Sclerochloa of others) covers the soil with a dense tuft of its
decumbent and floating stems. But sometimes the level is
higher and only occasionally submerged. Then the vegetation
is like that of the grey dune, characterised by its lowness, which
dwarfing may be accounted for by drought, aggravated by a high
degree of salinity and the exposure to wind : Salicornia her-
bacea, Suaeda maritima, Statice limonium (Sea Lavender), Aster
tripolium, Inula crithmoides (Golden Samphire), Spergularia
media (Sand Spurry). A very slight rise of the level gives origin
to the growth of Atriplex portulacoides (Sea Purslane), whose
silvery grey leafage fringes very prettily shallow stretches of
Salicornia and Suaeda. In autumn, when the latter turn deep
red or rich purple, a brilliant picturesque effect rewards the
botanist who visits the marshes in that season.
The next zone is the least stable and the least defined. Lying
at a level perhaps only a few inches above the former, flooding
by the tide occurs still more rarely. There are several tracts
of land on the Clacton coast which represent this zone. In
ditches and muddy hollows occur Salicornia, Aster, Triglochin
maritimum (Sea Arrow-grass). But then follow large patches
of land occupied by Scirpus maritimus and Juncus compressus,
both gregarious and excluding nearly all other plants, where