200 THE COAST-FLORA OF THE CLACTON DISTRICT.
whereas the ordinary observer will content himself by stating
what seems to be the dominant fact. However, the importance
of water and transpiration in plant-life is so transcendent that
any amount of chemical analyses and microscopical research
can do no more than amplify and render more precise the notions
got by ordinary observation.
The study of the sea-shore vegetation, as of any other,
falls naturally under two heads :
1. The floristic study, comprising the classification of the
species into different associations.
2. The study of the economy of those species and associa-
tions, naturally subdivided into
(a.) The study of the ecological factors : light, heat,
atmospheric precipitation, physical and chemical
properties of the soil, including water, and
(b.) The study of growth-forms, morphological and
anatomical peculiarities which must be regarded
as adaptations to the action of the ecological factors
mentioned.
The order in which I proceed is, perhaps, not strictly scientific ;
I shall treat first of the prominent ecological factors, soil,
water and salt, and then describe the various associations,
floristically and morphologically.
The soil of the coast is of two kinds : (1) sandy or gravelly
soil, occurring both on the valley gravel cliff from Clacton to
Holland and on the foreshores and low dunes on the coast stretch-
ing from Clacton to Colne Point and further. The particles
composing this soil being large and loose, its power of retaining
atmospheric precipitation is as small as its power of raising
water from moister subsoils. It is well aerated. In the sun
it is heated easily, but loses its warmth as easily at night : in
no soil are the alternations of temperature so pronounced
as in sand. The particles are small enough to be carried away
by the wind ; we observe the beginning of a dune at various
places. Chemically the nutritive value of a pure sand is
lowest of all soils. Sand mixed with gravel is not mobile, but
more liable to be heated. On the cliff it forms an extremely
unreliable support for plant-life, and is providing continually
new surfaces by crumbling down. When artificially supported
by a sea-wall, or the plantation of Tamarix, it becomes more