116 VEGETATION OP THE PEAK DISTRICT [CH. 



II. GRASSLAND OF THE LIMESTONE: CALCAREOUS GRASSLAND 



In previous works on British plant geography, this group 

 of associations has been variously termed "natural pasture," 

 "limestone hill pastures," and "Permian common" (cf. Smith 

 and Moss, 1903 ; Smith and Rankin, 1903 ; Lewis, 1904 a and b; 

 and Moss, 1907 a); but the name calcareous grassland is now 

 becoming general. 



Typical calcareous grassland consists of short, grassy turf, 

 largely composed of the sub-aerial parts of the sheep's fescue- 

 grass (Festuca ovina). In this district, calcareous grassland is 

 found abundantly on the uncultivated, steep slopes of the lime- 

 stone dales (see figures 12 and 16). On the limestone plateaux, 

 the soil is frequently leached, and then certain plants of the 

 siliceous grassland enter the association. 



It will be seen that the boundaries of the associations of the 

 soils of the sandstones and shales and of the soils of the lime- 

 stones do not follow any boundaries shown on the geological 

 maps. The latter indicate the boundaries and extent of the 

 subjacent rocks, but do not attempt to deal with the surface 

 soils which alone are related directly to the flora and vegetation. 

 This distinction between the subjacent rocks and the surface 

 soils is adequately emphasized in the treatment of plant 

 formations of the British Isles by Tansley (1911, passim). 



With slight differences in floristic composition as are indi- 

 cated in the preceding paragraph, calcareous grassland occurs 

 on all the uncultivated tracts of the various calcareous soils of 

 the country, such as on the chalky boulder clay, the chalk rock 

 and marl, the Jurassic marls and limestones, the Permian or 

 Magnesium Limestone, and the Palaeozoic limestones. 



Calcareous grassland is a plant association, or perhaps a 

 group of closely allied associations, characterized by the presence 

 of numerous lime-loving species and by the absence of heath- 

 loving or humus-loving species. Lime-loving species have been 

 variously termed xerophiles, calciphiles, and calcicoles: lime- 

 shunning species have been termed hygrophiles, calciphobes, 

 and silicicoles. It seems highly desirable to subdivide the 

 lime-avoiding species into three classes: (1) plants of acidic 

 peat, (2) plants of siliceous soils, and (3) plants of sandy soils. 



