158 Sub-formation of the Older Limestones 



occurring on the calcareous pasture, and also on limestone 

 cliffs in Derbyshire. 



In the west of England Melianthemum poUfolium, 

 Trinia glauca, and Koeleria vallesiana occur locally on the 

 calcareous pasture of the limestone hills. 



A larger number of species characterise the chalk of 

 south-eastern England and have failed to reach the 

 limestones of the west and north. 



Although swamps are less characteristic of calcareous 

 than of siliceous pasture, they do occur here 

 swamps ^^^ there on the slopes of the fissured 



limestones, and they are characterised by 

 different plant communities from the swamps of siliceous 

 soils. On the Pennines, for example, the following plants 

 occur on the swamps of the limestone hills : 



In exposed situations, especially on plateaux and the 

 The " Um higher hill-slopes, the soil of the calcareous 



stone heath." Pasture tends to lose its high lime-content 

 owing to the leaching action of rain. As this 

 process continues, some of the plants of siliceous grassland 

 may invade the leached area, and in time, a limestone 



