200 VEGETATION OF THE PEAK DISTRICT [CH. 



remain white ; and the presence of black or white stone fences 

 is a convenient indication as to whether one is in the area of 

 sandstone or of limestone respectively. 



Hedgerows in the Pennine district are rare, and only occur 

 where the shales are of great superficial interest, as, for example, 

 near the confluence of the rivers Noe and Derwent. 



At its upper limit, the permanent pasture frequently abuts 

 on the uncultivated grassland. A distinction is made on the 

 Ordnance maps between " land under cultivation " and " land 

 not under cultivation"; but, at and near the upper limits of 

 cultivation, the boundaries shown on the Ordnance maps are 

 not always reliable. A comparison of the boundary line between 

 cultivated and uncultivated land as shown respectively on the 

 Ordnance maps and on the accompanying vegetation maps will 

 reveal rather considerable discrepancies. 



I am unaware of the principles used by the Ordnance 

 surveyors in making this distinction. In the present vegeta- 

 tion survey, the plan has been to make lists of the species of 

 the difficult tracts, and compare the lists thus made \vith lists 

 of tracts which are indubitably uncultivated or cultivated, as 

 the case may be. There are, without doubt, many areas with 

 regard to which there may be difiPerences of opinion as to whether 

 or not they should be mapped as land under cultivation ; but 

 this does not explain all the details of the mapping of the 

 Ordnance surveyors, who, indeed, are sometimes very incon- 

 sistent even on the same " six-inch " quarter-sheet. 



On the accompanying vegetation maps, the grassland not 

 considered to be cultivated, although it may be more or less 

 grazed, is coloured as siliceous grassland when the flora contains 

 many heath-loving or humus-loving species, and coloured as 

 calcareous grassland when there are many lime-loving species 

 present. These two associations or groups of associations have 

 been discussed in the chapter on grasslands. Some of the 

 enclosed fields have apparently once been cultivated and have 

 been allowed to become derelict ; and such areas, by the in- 

 vasion of plants from the uncultivated land, gradually approach 

 in character to the neighbouring subspontaneous or spontaneous 

 associations. However, up to about 1250 feet (379 m.) the 

 cultivated fields may generally be kept in good condition 

 without much difficulty ; and one frequently sees, even at the 



