SURVEY AND COMPARISON 178
Species found in both areas include:—
(i) Puccinellia maritima. This species appears to require
a high salinity and an expanse of soft, stable mud.
It is not found on small ledges of mud, nor in positions
where it is in danger of being immersed for long
periods.
(ii) Salicornia species. All theae require a high salinity,
and all except S. Smithiana will only grow on mud
which is softened by continual tidal movement or by
the mixing with creek water which results from
trampling of the banks by cattle. These species can
tolerate longer immersion than Puccinellia. S.
Smithiana is tolerant of drier conditions and flourishes
on dry, cracking mud.
(iii) Suaeda maritima. This is a species of high salinity
requirement, but it is tolerant of varying drainage
conditions. It occurs with Salicornia spp. on the
softened mud. in drier conditions at the base of the
sea wall, and in very dry creek beds.
(iv) Aster Tripolium needs very saline, wet and rather
stable conditions. Presumably, the weight of the
fully-developed plants prevents it from colonising
small ledges of trampled creek banks. There seems
no obvious explanation for the presence of ray florets
in the Aster of the inned marsh, and the absence of
these in the plant of the natural marsh.
(v) Triglochin maritimum. The presence of this species
is determined by high salinity. It is tolerant of dry
conditions on the inned marsh and very wet ones on
the natural marsh.
(vi) Spergularia species. These require fairly saline con-
ditions, but will grow in fairly dry places at the
margins of the arable land and in very muddy parts
near Creek 4 and on the natural marsh.
Of the species confined to the inned marsh, the following
are most important:—
(i) Scirpus maritimus. This is a species very tolerant
of varying conditions of drainage and salinity. Since