of blown sand, carrying some typical dune plants, can be seen in the Breckland. All plants capable of establishing themselves in mobile sand bear a general resemblance to each other wherever they occur, and the majority of them are known as xerophytes (Greek xeros=dry). Most of them possess unusually extensive roots or rhizomes (buried stems), and their leaves are often adapted in some way or other to cut down excessive loss of water from them. Many xerophytes have succulent leaves and stems, similar to those belonging to halophytes. This likeness, is, however, largely accidental and is due in this case to the development of water-holding cells, called collectively “aqueous tissue” (see page 47), for the purpose of storing water. Xerophytes are by no means confined to dune areas in Britain but may also be found in other dry habitats inland. Those confined to dunes, besides possessing an unusual ability to withstand drought, are also able to deal with the problem of occasional burial in loose sand by their exceptional powers of sending up new shoots as soon as they are covered over—marram-grass (Fig. 10) possessing this power to a quite remarkable degree. Other familiar examples of dunc-xerophytes are sea-holly (Eryngium maritimum) (Pl. 1) and sea-sandwort (Honckenya peploides). Shingle beaches and dry cliffs are other coastal habitats where plants of this group commonly occur. The characteristic form and habit adopted by both halophytes and xerophytes is discussed in greater detail in Chapter 4.
The remainder of the plants to be seen in the coastal belt are too numerous and varied for it to be worth while attempting further classification. Practically all types of inland vegetation are represented somewhere along the coast, although woodland is virtually absent from all exposed situations and is confined to the borders of sheltered estuaries or to deep valleys (or coombes) which have been cut through cliffs, where sufficient protection from the wind is provided. Typical marsh plants, for instance, grow in the wet “slacks” sometimes found between ranges of sand-dunes (Pl. XXII), and in north-west Scotland and Ireland, alpine plants, characteristic of the higher mountains in Britain, occur near sea-level on the cliffs and beaches just as they do farther north in sub-arctic regions. Nor is it surprising that a large number of common plants, usually associated with dry waste-places of all kinds, find a home on the older stabilised dunes and shingle beaches, particularly shallow-rooted annuals, which can pass through their life-cycle during the winter and spring, before the advent of the summer droughts.
There are, however, a number of what may be called “sub-maritime” plants, which are neither halophytes nor xerophytes, but seem rarely to be found more than a few miles from the sea. Well-known examples of these are the slender thistle (Carduus tenuiflorus), alexanders (Smyrnium olusatrum) (Pl. IV), fennel (Foeniculum vulgare) (Pl. XXXIV), and one of the mouse-ear chickweeds (Cerastium tetrandrum). Besides these, there is a much longer list of species which, though not confined to the coastal belt, are always far commoner there than farther inland. Storksbill (Erodium cicutarium) and buck’s-horn plantain (Plantago coronopus) (Pl. XXXVI) are familiar examples. None of these plants conform to any special type (there are a number of aquatic plants as well) and no explanation is at present forthcoming to account for their distribution (see here).
It is unavoidable in a book of this kind that it should contain a large number of lists of the plants usually found in the various habitats. These may well seem tedious to some readers who are unfamiliar with the appearance of many of the species mentioned, and I have therefore devoted Chapter 12 to giving brief popular descriptions of plants mainly confined to the coastal belt. I have also added notes on their distribution and their relative importance in the general vegetation. It should be clearly understood, however, that it is in no sense my object to provide a flora for identifying all the plants likely to be encountered along the coast, and I have not attempted to include those species which are equally common inland. A number of standard floras are mentioned in the Bibliography (see here), and one of these should be consulted when identifications are being made. At the same time, it is to be hoped that this chapter may prove useful for quick reference. The main object of this book, however, is to describe seaside vegetation as a whole, and to relate it as far as possible to the various habitats where it is found.
I have devoted a separate chapter to the vegetation found in each of the main habitats. The following summary will give some idea of particular portions of the coast with which we shall be concerned in each chapter:
1. SALT-MARSHES (Chapter 5)
The mud or sand of the inter-tidal zone on flat shores, which is sufficiently protected from violent wave-action to support vegetation, including areas only flooded by the highest tides.
2. BEACHES AND FORESHORES (Chapter 6)
A comparatively narrow zone along the tops of exposed beaches of any material, other than rocks, only reached by the highest tides.
3. SAND-DUNES. (Chapter 7)
All areas of sand, originating in material blown by the wind from the shore, from shifting open dunes just beginning to accumulate round individual plants, to old and mature deposits whose surface has become almost completely stabilised by a close cover of vegetation.
4. SHINGLE BEACHES (Chapter 8)
The beaches, bars or spits of water-worn pebbles, derived from rocks by wave-erosion and deposited by the sea on low-lying shores. These vary from highly unstable banks of stones, continually shifted by the waves, to the oldest beaches where the shingle is completely dormant and has long been isolated from any wave-action.
5. CLIFFS AND ROCKS (Chapter 9)
Rocky places above the high-tide mark or cliffs of any material, which are to some extent exposed to salt spray. Certain artificial habitats such as sea-walls, which are similarly exposed to spray, are included in this category.
6. CLIFF-TOPS (Chapter 10)
The strip of ground along the tops of cliffs, exposed to a certain amount of spray and often supporting some characteristic sub-maritime plants as well as maritime and inland species. When the tops are level this is usually quite narrow, but on steep slopes it may cover a large area and then differs from the cliff habitats in the previous chapter only in possessing more soil.
7. BRACKISH WATER (Chapter 11)
The swamps, ditches, lagoons, or estuaries of slow-moving rivers where the water remains brackish as a result of sea-water mixing with fresh water. These are often inhabited by a characteristic mixture of sub-maritime and inland aquatic plants.
It is hardly necessary to add that these habitats are by no means always sharply separated, but in many places overlap considerably. Sand-dunes, for instance, often grow up on the crests of shingle ridges, and salt-marshes develop easily behind the protection of shingle or sand-bars. As a result, the vegetation is often mixed up in a distinctly confusing manner—nowhere better seen than along the north Norfolk
