146 Suh-formation of the Older Limestones 



limestones are the chalk (southern, eastern and north- 

 eastern England), the Oolitic limestones of the Jurassic 

 series (west midlands), the Magnesian Limestone of 

 Permian age (northern England), the Carboniferous or 

 Mountain Limestone (Pennines, Wales and Somerset), and 

 various Devonian limestones in Devonshire. Limestone 

 strata of minor importance occur in rocks of all ages. 

 In Ireland the Carboniferous Limestone has a very wide 

 extension, and though it is frequently covered with non- 

 calcareous deposits, it is exposed over considerable areas 

 in the west; but in Scotland there are no extensively 

 developed rocks of this class, though minor limestone 

 bands occur. Same of the soils derived from igneous 

 rocks rich in lime-containing minerals, such as some of 

 the felspars, are also calcareous. 



Though there are more or less important floristic and 



ecological differences between the vegetation 

 formations °-^ ^^^ chalk, which is mainly developed in 



the drier regions of the east and south, and 

 that of the older limestones, which are mainly developed 

 in the wetter regions of the west and north, yet these do 

 not seem of sufficient importance to override the essential 

 unity of the limestone vegetation as a whole. We shall 

 therefore consider the whole of this vegetation as con- 

 stituting a single formation, regarding the vegetation of 

 the older limestones as one sub-formation, that of the 

 chalk as a second and that of the other calcareous soils 

 as a third. 



The Sub-formation of the older Limestones 



By C. E. Moss 



By far the most extensive of the older limestones is 

 the so-called Mountain Limestone of carboniferous age, 

 which forms the centre of the Pennine Range, occurs in 



