PLANTS AS STABILIZERS
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ward fetch considerable, wave action may have an analogous effect, with the result that the beach undergoes local attrition. Examples of this are included in our chapter on Blakeney Point (pp. 233, 237).
   D.	Uncovering.—A fourth source of erosion to which shingle beaches are liable is exposure or uncovering, owing to the sand dunes which encumbered them being blown away. Some beaches acquire a covering of sand-hills pari passu with their formation, and as the tip advances the source of sand on the foreshore moves forward in sympathy. Under these circumstances the dunes are starved of sand, so that losses are not made good. Should the dunes become inhabited by rabbits, and this is generally the case, they will in time be blown away unless they have been planted with pines or other ligneous vegetation. The areas of shingle thus exposed are very sterile and difficult to colonize with plants, and, if suitably placed, they are liable to erosion through wave impact.
   The Plant Covering and its Stabilizing Effect.—Though it rarely, if ever, happens that plants which spontaneously colonize mobile shingle beaches so dispose themselves as effectively to render the beach absolutely dormant, nevertheless the matter deserves the most careful study, for it is patent that by following Nature’s lead this result is to be reached.
   The number of species of plants to be found growing wild on shingle beaches in various parts of Britain is considerable, 120-150 perhaps. The seeds of these arrive by various agencies —tidal drift, wind, by means of birds, and no doubt by unconscious human agency. In addition to the above, which arise and establish from seed directly on the beach, there is a further element derived from the terrains (marshes, pastures, &c.) which the beach overruns in its landward travel. Certain of the plants of these grow through the invading shingle, take root therein and lose connection with their original ground. Such plants may be termed Anarhizophytes.1 Of all
    1 The term anarhizophytt ;s suggested for any plant having the capacity to root in terrain which invades and overlies its original habitat or place of establishment. This capacity is widely spread and plays an important part in Nature. Suceda fruticosa on shingle, Psamma on sand dunes, and Armeria and other perennial halophytes of the salt marsh are outstanding examples from the seashore.
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