122 VEGETATION OF THE PEAK DISTRICT [CH. 



Analogous vegetation occurs, of course, on the grasslands 

 of the sandstones and shales. However, the details of British 

 grassland associations, or groups of associations, have not yet 

 been fully investigated. 



On the limestone plateaux, such tracts of grassland are 

 frequently characterized by the great abundance of the mountain 

 pansy (Viola lutea and V. lutea var. amoena), which, in early 

 summer when the plant flowers with great exuberance, gives 

 rise to a distinct facies or aspect. 



Transitional Calcareous Grassland 



At still higher altitudes (about 1100 feet = 335 m.), a type 

 of pasture occurs which is transitional between calcareous 

 grassland and siliceous grassland. A certain number of heath- 

 loving or humus-loving species, such as Luzula multiflora, 

 Potentilla erecta, Poly gala serpyllacea, and even Ulex Gallii, 

 and also a certain number of lime-loving species, particularly 

 Poterium Sanguisorba, may occur; and, under these circum- 

 stances, such grassland may be regarded as transitional between 

 calcareous and siliceous grassland. Such grassland occurs also 

 on the Carboniferous Limestone in Yorkshire. Analysis shows 

 that the superficial soil of such localities is comparatively poor 

 in lime, even when the subsoil consists of limestone, and, as 

 stated in the introductory chapter, even when there are no 

 glacial or other foreign deposits. Doubtless the soil, in the 

 course of ages, has had much of its lime carried away in 

 solution. This type of grassland is, on the vegetation maps, 

 given the same colour as that used for siliceous grassland. 



CALCAREOUS HEATH 



Where the lime-content of the superficial layer of soil is 

 still lower, such dwarf-shrubs or under-shrubs as the heather 

 (Calluna vulgaris) and the bilberry ( Vaccinium Myrtillus) may 

 occur ; and thus transitions occur between calcareous grassland 

 and heath. This transitional association may be termed a 

 calcareous heath. The association occurs on the Carboniferous 

 Limestone in Somerset (Moss, 1907 a : 46), usually at altitudes 

 above 600 feet (183 m.), below which altitude, typical calcareous 



