OBSERVATIONS OF PLANT FORMATIONS 19 



The two lines of seaweeds are clearly seen on shingle beaches ; 

 one line marks the high water at the last spring-tide ; the other 

 is the high-water line of the last tide. 



The pebbles which have seaweeds attached to them have 

 probably been pulled to their position by the seaweeds. 



The characteristics of plants belonging to the shingle may be 

 ascertained by comparing them with each other. 



6. In observing the vegetation on cliffs the geological character 

 of the rock should be ascertained before it is possible to compare 

 one flora with another. It is easy to distinguish stratified from 

 unstratified rocks. Granite is unstratified, limestone stratified. 

 To some limited extent it is possible to recognise rocks by their 

 colour. Chalk is white ; unweathered clay is blue, but the action 

 of the atmosphere on it gives it a yellow tint, and the effect of 

 burning it is to convert it into a brick-red. The old red sandstone 

 is red in colour, but red may also denote the presence of iron ; it 

 is not therefore safe to depend on colour alone. Limestone may 

 be detected by testing with a strong acid ; a piece of limestone rock 

 effervesces when hydrochloric acid is poured on it. A geological 

 map of a district will give the geological formations, and enable 

 any one to ascertain the nature of the cliffs. 



The plants belonging to each kind of cliff can only be a matter 

 of gradual observation. Lists should be made of the plants found 

 at different seaside places, and compared with each other. It is 

 impossible to generalise until a great many places have been 

 visited. It will be found that some plants are common to all 

 shores ; for what they want is salt. To determine in any particular 

 case whether the plant requires salt or not, it may be transplanted 

 to ordinary garden soil and watched. If it thrives without any 

 addition of salt to the soil, it is independent of salt ; but the 

 majority of plants growing by the sea will not flourish in an inland 

 garden unless the soil is watered with a solution of common salt. 



OBSERVATIONS OF PLANT FORMATIONS. The Plant associations 

 occurring in the different belts of the shore should be carefully 

 noted in this order : i. Those nearest to the sea, whether on 

 cliff or in mud or on sand. These are open associations. 2. The 

 Intermediate associations, which may be two or three in number, 



