124 PLANT-LIFE ON LAND [ch. 



A peculiar vegetation, however, appears in parts 

 of the coast-line where a sandy beach leads up to 

 a more level land-surface, and solid rock is absent, 

 or at least discontinuous, or covered out of sight. 

 There in the inlets and bays, or along considerable 

 lengths of the shore, may extend those lands claimed 

 by the Golfer as the only true "Links," protected 

 seawards by rougher Sand-hills or " Dunes." Lastly, 

 between these and the tide-marks there is usually 

 a narrow, but more or less level expanse of dry sand, 

 which may bear its own limited but interesting Flora. 

 The substratum of the Links and Dunes is all com- 

 posed of sand, with here and there it may be projecting 

 bosses of the underlying skeleton of solid rock. The 

 sand of the Dunes is entangled with rough Marram 

 Grass. That of the Links is mostly covered by a 

 continuous but thin sod, matted with a dense growth 

 of smaller plants. 



Sand-hills or Dunes may be formed by the action 

 of the wind alone. Examples are seen in various 

 localities, but they have been studied Avith special 

 care in the Libyan Desert, where the wind-formed 

 Dune takes a very definite crescentic shape styled 

 a "Barchan" (Fig. 19). The moulding of the wind- 

 formed Dune is commonly such that a gradual slope 

 of 5 — 10 degrees on the windward side leads up to 

 a ridge, from which the surface again falls Avith a 

 slope of about 30 degrees on the leeward face. But 



