130 PLANT-LIFE ON LAND [CH. vm 



plants provide those local shelters in which the 

 moving sand collects. But as many of these plants 

 are annuals, while none grow to any considerable 

 height, they are not efficient in securing permanence, 

 or in promoting any considerable rise of level of 

 sand collected. The result is that the areas they 

 cover are usually flat, and slope directly down to the 

 general level of the beach. Their eifect is thus apt 

 to be local, and insignificant when compared with 

 that of the more efficient sand-binders of the Dunes. 

 Nevertheless the methods of action of these plants 

 are well worthy of observation and study, both from 

 the point of view of the self-preservation of the 

 plants under their peculiar surroundings, and as 

 regards the practical binding effect which they 

 produce. 



Next in order landward come the Dunes, which 

 rise more boldly from the level of the beach, but as 

 often as not they abut directly upon the high water- 

 mark, and the lower growths just described may be 

 entirely absent (Fig. 22). The Dunes that face the 

 sea are usually " White Dunes " : that is, the sand is 

 not covered in by vegetation, but is largely exposed, 

 so that the colour of the whole is that of the sand 

 itself rather than of the plants growing upon it. 

 They commonly present a steep face to the shore, 

 sloping more gently on the landward side. This is 

 probably due to their growth seawards being re- 



