390 ECOLOGY 



shingle beach may be replaced by a closed association 

 of pasture species. 



The conditions chiefly affecting plant-life on the coast 

 are mobile soil and salt water. On the disturbed ground 

 the plants are usually annuals ; anchorage is secured by 

 deep-growing tap-roots, and the long rhizomes and numerous 

 adventitious roots of perennials serve as binders for the 

 loose soil. The shoots are liable to be buried, but their 

 great power of rejuvenescence enables them to keep above 

 the surface and aid in building up banks of sand and shingle. 

 The plants have usually a low habit, whereby the tearing 

 effect of the wind is reduced. The shoots are modified in 

 many ways : the stems and leaves may be spiny ; the 

 leaves are often small or reduced by rolling ; fleshy plants 

 are common, and the epidermis is covered by a grey waxy 

 bloom or by hairs. In some species the hairs become 

 detached and form a ' meal ' on the surface. By such 

 modifications the stomata are protected, transpiration and 

 radiation reduced, and the water-supply conserved. Plants 

 possessing these modifications are able to survive the con- 

 ditions of the habitat, and they give a characteristic 

 appearance to the vegetation of the coast. 



CHAPTER XXXIV 



MOORLAND AND ALPINE PLANTS 



Many of our English moorlands occupy the sites of former 

 woodland or scrub, and are extensively developed on the 

 Pennines and on the Cleveland Hills. Two distinct types 

 occur : (i) the Cotton-grass moor (Fig. 250) and (2) the 

 Heather moor (Fig. 251), but these are connected by several 

 intermediate phases or transition types. 



