158 THE ESSEX NATURALIST
tide, but a certain amount of water remains in the
central part of the marsh, left behind by the rapid fall
of water in the creeks. Thus the margins of the
marsh are well drained and the central parts are
always water-logged. In many places in this part,
a little water stands continuously.
Results show that the chloride content of the main salt
marsh is high and fairly constant, affecting all species to a
similar extent. The drainage is, however, much more
efficient at the margins of the marsh, and this causes the
formation of two zones of vegetation.
The marginal zone is up to three yards wide and is
covered almost exclusively with Halimione (Obione) portula-
coides (L.) Aell. In many places this is a foot or more high,
and forms a dense and tangled cover. Where the creek banks
are steepest, H. portulacoides roots at the top of the bank
and overhangs the edge.
The central zone is dominated by Puccinellia maritima
(Huds.) Parl., which forms prostrate mats over the wet
ground. The main species associated with the Puccinellia
are Suaeda maritima (L.) Dum., Aster Tripolium L., and
various species of Salicornia. These plants all occur in
patches scattered generally in the Puccinellietum. The
Aster here rarely shows any purple ray florets. The
Salicornia species represented include S. perennis (Gouan)
Mill., S. dolichostachya Moss, S. stricta Dum., and S.
ramosissima Woods. Averages of quadrats on this part of
the marsh show that a percentage of the ground covered by
the main species is as follows:—
Puccinellia maritima ... ... 75.0%
Suaeda maritima ... ... 10.0%
Aster Tripolium ... ... 8.5%
Salicornia spp. ... ... ... 2.5%
Spartina Townsendii H. & J. Groves occurs in this central
zone in a number of isolated, characteristically round,
patches. Limonium vulgare Mill., Triglochin maritimum L.,
Plantago maritima L., Spergularia rubra (L.) J. & C. Presl.
and Cochlearia anglica L., also appear in a few scattered
patches. Armeria maritima (Mill.) Willd. occurs once in an