THE COAST-FLORA OF THE CLACTON DISTRICT. 201
stable and gives rise to a different vegetation more resembling
that of the clayey cliff.
2. Muddy or clayey soil is in many respects the exact
counterpart of the sandy soil. The particles are finer and more
cohesive; its power of retaining water very great. When
exposed to prolonged drought, however, it becomes as hard as
stone, thus rendering absorption of water practically impossible.
Like the sandy soil it occurs in different heights from the sea-
level, e.g., in the creeks and muddy flats, then on dams which
have been erected against the inrush of the tide into the reclaimed
land, and on the cliff itself.
Plants growing on sandy soil are called Psammophytes or
Psammophilus (sand-loving) plants and those preferring
muddy soil Pelophytes or Pelophilous (mud-loving) plants.1
Salt.—The physical nature of the soil does not, however,
yield the only fundamental test by which to divide the coast-
flora. The action of the salt contained in the sea-water is
another. There are plants that are obviously dependent upon
being more or less often reached by the tide, and whose soil
and tissues contain a varying amount of chlorine. These
are called Halophytes or Halophilous plants. There are Psam-
mophilous and Pelophilous Halophytes. On the other hand
plants grow on the shore that have no need or predilection for
salt and might grow inland, if they found convenient soils. Thus
Salicornia (Marsh Samphire) is a Pelophilous Halophyte, Cakile
(Sea-rocket) a Psammophilus Halophyte, while Psamma
arenaria (Sea Marram) is said to be a non-Halophilous Psammo-
phyte, being able to grow quite well at a great distance from
the sea, if it can find shifting, deep sand to grow upon.
The percentage of salt in different places varies according
to the number of submersions by the tide, the number and
violence of storm-splashes (on sea-walls and cliffs), the amount
of fresh water introduced either by atmospheric precipitation
or by the raising of ground-water and the facility of drainage.
Obviously a depression at a high level, although reached only
by an exceptionally high tide, may by evaporation become more
saline than the parts exposed to the daily scour of the brine.
It must be kept in mind also that the salinity varies, not only
1 This nomenclature is taken from the recent standard-book of Warming: The Ecology
of Plants.