12 



THE BOOK OF NATURE STUDY 



tion of plants. A new railway line presents endless opportunities. 

 The plants coming up on the embankments the first season after 

 the line has been laid down will be ousted in succeeding seasons 

 by others, and it is interesting to trace the spread of any particular 

 species along the line, or the extermination of species by successful 

 rivals in the struggle always going on for existence. 



CLIFF VEGETATION. The vegetation of rocky headlands 

 depends mainly on two factors : the nature of the rock and the 

 latitude. Where the rock is hard and massive, as in the case of 

 granite, Jhe vegetation is scanty and far less luxuriant than it is 

 on limestone cliffs. With regard to latitude, the plants which 

 are common in such a southern county as Somerset are scarce 

 off the coast of Northumberland, and are not found beyond the 

 latitude of Edinburgh. 



The following table shows at a glance the principal plants of 

 certain typical cliffs. 



VEGETATION OF CLIFFS 



CHARACTER OF ROCK. 



DOMINANT SPECIES. 



SUB-DOMINANT. 



Rough granite .. 



Slates and quartzites 



Carboniferous limestone 



Very scanty vegetation 



Sea Samphire 

 Sea Aster 

 Sea Beet 



Sea Samphire 



Chiefly Heaths and Furze. 



Sea Pink. 

 Sea Campion. 

 Sea Plantain. 

 Scentless Mayweed. 

 Scurvy Grass. 

 Tree Mallow. 

 Sandspurry. 



Sea Lavender ^ 



Scentless Mayweed I less 

 Sea Campion | abundant, 



Scurvy Grass 



Slate rocks are cut by the action of the waves into all kinds of 

 shapes, and the vegetation in the cliffs and on the ledges of the 

 rocks, where sand or other soil has been deposited, is sometimes 

 luxuriant. The dominant plant is usually the Sea Samphire 

 (Crithmum maritimum). This has a short zigzag stem and very 

 much divided leaves, the narrow segments of which stand upright. 



