128 PLANT-LIFE ON LAND [CH. 



quiet spot. Such quiet spots are found under the 

 lee of any obstacle, such as a stone, a seaweed, or 

 a living plant. Any one who observes the beach after 

 a high wind, especially if it blew in a direction follow- 

 ing the coast-line, will find innumerable instances 

 of the sand-streamers which thus collect under the 

 lee of any solid object, living or dead (Fig. 20). But 

 if the object itself be a living organism, and grows 

 upwards as the sand collects around it, then there is 

 the possibility of an actual building up of a permanent 

 heap, provided that the winds recur at intervals. 

 This is the principle which underlies the origin of 

 all permanent sand-formations on the coast, and the 

 conditions are sometimes repeated inland. It is 

 the presence of certain sand-dwelling plants which 

 provides in the first instance the sheltered spots for 

 the settling of the sand, and secondly, it is by their 

 continued growth that that degree of permanence 

 and enlargement is secured which is characteristic of 

 the Dunes and Links as compared with mere shifting 

 sands. 



We may take the formations thus built up from 

 the sand in the order in which they severally present 

 themselves as we pass upwards from the high-tide 

 mark. First, there may be a zone of loose sand, dry 

 at the surface and easily shifted by the wind. 

 Spreading downwards into it, and not much, if at 

 all, raised above the beach, comes the advanced 



