MARITIME ASSOCIATIONS 283 
becomes a calluna-heath, or a heath dominated by Salix 
repens. 
Dune-Marsh.—In the hollows amongst the dunes 
water collects, and a fresh-water marsh develops. It 
differs in no important respect from an ordinary marsh, 
except where the sea has access to it, when it is inter- 
mediate in character between a fresh-water marsh and a 
salt-marsh. 
3. Pebbly and Shingly Beaches.—These differ from a 
sandy beach chiefly in the greater abundance of inland 
plants and the scarcity of grasses with underground 
creeping rhizomes, which are so characteristic of sand. 
The following zones met with on some pebbly beaches 
of the south coast of England may be taken as typical of 
such beaches in general: | 
Nearest the sea is a zone of Atriplea hastata. Behind 
this a narrow zone of Rumex crispus, associated with 
which are Glaucium luteum, Solanum Dulcamara var. 
marinum (forming a mat close to the ground), Senecio 
Jacobea, and various species of Atriplex. Farther back 
Ulex europeus is dominant, with Silene maritima very 
abundant, and a few specimens of Galeopsis Ladanum var. 
canescens. Between this zone and the Rumex-zone occur 
many scattered plants of Beta maritima, Galium Mollugo, 
Teucrium Scorodonia, and Silene maritima. Behind the 
zone of Ulex the plants are again scattered. In addition 
to the foregoing, Daucus Carota, Echium vulgare, and 
Leontodon hirtus occur. In places the Ulex-zone is absent, 
the vegetation behind the Rumex-zone consisting of 
scattered plants of Dianthus prolifer, Geranium Roberti- 
anum var. purpureum, Glaucium luteum (very abundant), 
Galium Aparine, and G. Mollugo, Matricaria inodora var. 
salina, and Helminthia echioides. 
Where the beach is more sandy Eryngium maritimum 
becomes dominant, and associated with this are Arenaria 
peploides, Trifolium arvense, Crithmum maritimum, Silene 
maritima, Spergularia marina, Beta maritima, Rumex 
crispus, Senecio Jacobea, Crambe maritima, and Daucus 
Carota. 
All the inland plants or their varieties develop much 
thicker, succulent leaves than when growing in their usual 
habitat. 
4. Rocks and Cliffs—The vegetation of rocks which 
