20 THE BOOK OF NATURE STUDY 



and are on the landward side of the open associations nearest 

 the sea. 3. The Pasture associations. These comprise the 

 plants of (a) The sand-dune pasture ; (b) the salt marsh ; (c) the 

 cliff. In all these pastures, many seashore plants will be found, 

 for the spray is blown by the wind some little distance inland 

 and the plants thus get the salt they require. 



The best way of getting an idea of the way in which a Plant 

 formation arises is to watch the colonising of a new piece of 

 ground, as, for instance, a railway embankment along a newly 

 made line. The first plants to appear should be recorded ; then 

 their destruction by other plants. The gradual migration of 

 plants into a new district from an adjoining area is an observation 

 full of interest. 



BIBLIOGRAPHY. Lord Avebury, Scenery of England ; Pethybridge, "Vegeta- 

 tion South of Dublin" (Proceedings of the Royal Irish Academy, December 1905). 



