162 THE ESSEX NATURALIST
On the flattened top of the wall, the species of the sloping
sides are replaced by those which can withstand a certain
amount of trampling. These include Poa pratensis Ij.,
Lepidium ruderale L. and Polygonum aviculare agg.
At the top of the landward slope. Atriplex littoralis is
again frequently found, but the main dominant of the whole
slope is Agropyron pungens. Beta maritima again occurs
near the top of the wall, but it is less frequent here than on
the seaward side. Further down the slope, scattered plants
of Vicia angustifolia (L.) Reichard, Lactuca serriola L.,
Medicago arabica (L.) All. and Leontodon leysseri (Wallr.)
Beck appear amongst the Agropyron, and at the base near
the bank of Creek 4 the species present with Agropyron
include :—
Arrenatherum elatius. Lolium perenne.
Bromus mollis. Plantago lanceolata.
Daucus carota. Potentilla reptans.
Festuca rubra. Senecio Jacobaea.
Holcus lanatus. Trifolium campestre.
Between Sites 4B and 40 about 20 bushes of Crataegus
monogyna Jacq. occur near the base of the wall, and seed-
lings of this plant are scattered in this area. The development
of the community here, which has allowed for the growth
of these bushes, is probably favoured by the proximity of
this part of the sea wall to arable, rather than pasture, land.
A summary of the distribution of the species of the
undisturbed wall vegetation is given in the following
diagram :—