A Second Experiment in Ecological Surveying. 201 
to Sept. 10th) was organised on a considerably larger scale. 
Advantage was taken of the experience gained last year, and an 
area was chosen, easy to get about on, and with a very sharply 
defined characteristic flora consisting of comparatively few species, 
whose distribution was evidently largely dependent on certain phy¬ 
sical relations. The area in question is the estuary of a small 
stream, known as the Bouche d ’Erquy, on the north coast of 
Brittany, about twenty-five miles west of St. Malo. The estuary 
itself, about 150 acres in extent, is separated from the sea by a spit 
of old sand-dunes, which extends at right angles to the main 
direction of the river, and allows it egress by a comparatively 
narrow channel. The lower part of the estuary is covered with 
bare sand brought in by the tide and constantly shifting in position, 
but practically the whole of the upper part is occupied by a carpet 
of halophilous vegetation. The soil here is largely mud, though 
this is over-laid in places by sand brought up by the tide, and surface 
borings reveal constant alternations of sand and mud-layers. The 
highest parts of the estuary are only covered by water at the 
highest spring tides, i.e., for very few hours in the month. Rather 
lower tides cover more or less of its surface, while the lowest neaps 
are barely felt in the channel of the stream. There are three small 
tributary streams running through the estuary and emptying them¬ 
selves into the main river ; their channels, carved out and scoured by 
the tide, are cut through the gently undulating plateau which forms 
the general surface of the estuary and lies a few feet above the 
surface of the stream-beds. This plateau is also intersected by 
channels of varying depth, which do not serve for the passage of 
streams, but up which the higher tides run. 
The plateau is covered by plant associations, in which five 
species are dominant:— Salicornia herbacea, Glycerin maritima, 
Suaeda fruticosa, Obioue portulacoides and giutcus maritimus 
These five form the great bulk of the vegetation, while associated 
with them are Salicornia radicans, Spergularia marina, Aster 
Tripolium, Anneria vulgaris, Statice Limonium and others. The 
distribution of the associations, as has been said, is obviously 
dependent very largely on differences of level, but there are clearly 
several factors at work, and their elucidation presents problems of 
great interest. A very marked feature of the vegetation when it is 
at its highest point of development, in August and September, is 
the colour of the Salicornia and Suaeda. These plants vary from 
bright green to deep crimson, according to their place of gcowth, 
and the landscape effects produced are of very striking beauty. 
The immediate object of this year’s Expedition was to map 
