94 ROCK PLANTS OF THE PASTURES 



As a rule, the plants which grow on the rocky 

 portions of an upland pasture are not those which 

 abound in the normal pasture. We will devote 

 the present chapter to the rock plants of the pas- 

 tures, including with them those which grow under 

 similar physical conditions on the dry^ bare, stony 

 slopes. 



The study of the colonisation of bare ground or 

 virgin soil by plant life, whether at home or in the 

 Alps, is a most interesting occupation. Many will 

 have noticed how in England some artificially 

 made new ground suitable for plant life, such as a 

 railway embankment, becomes gradually populated, 

 the Coltsfoot being, as a rule, the first to seize upon 

 the opportunity to establish itself. In the Alps, 

 fresh areas of rock are constantly being exposed, 

 either by the washing away of the soil and its vegeta- 

 tion by streams, especially in time of flood, or by 

 avalanches in winter, or again by soil-slip, the ever- 

 present tendency of the soil of the sides of the valley 

 to slide downwards. In other cases, landslips on a 

 large scale not infrequently lay bare the rock of a 

 mountain side, which formerly was densely clothed 

 with vegetation. How do plants establish them- 

 selves on such new ground ? What are the first 

 species to take advantage of the fresh opportunity ? 



We have already called attention to the struggle 

 for existence, the competition for room, light, and air, 

 among Alpine plants. It follows that any opportuni- 

 ties will naturally be quickly seized upon, where fresh 



